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Learning Objectives
- To become familiar with the organization of the periodic table.
Rutherford’s nuclear model of the atom helped explain why atoms of different elements exhibit different chemical behavior. The identity of an element is defined by its atomic number (Z), the number of protons in the nucleus of an atom of the element. The atomic number is therefore different for each element. The known elements are arranged in order of increasing Z in the periodic table (Figure \(\PageIndex{1}\)). The rationale for the peculiar format of the periodic table is explained later. Each element is assigned a unique one-, two-, or three-letter symbol. The names of the elements are listed in the periodic table, along with their symbols, atomic numbers, and atomic masses. The chemistry of each element is determined by its number of protons and electrons. In a neutral atom, the number of electrons equals the number of protons.
The elements are arranged in a periodic table, which is probably the single most important learning aid in chemistry. It summarizes huge amounts of information about the elements in a way that facilitates the prediction of many of their properties and chemical reactions. The elements are arranged in seven horizontal rows, in order of increasing atomic number from left to right and top to bottom. The rows are called periods, and they are numbered from 1 to 7. The elements are stacked in such a way that elements with similar chemical properties form vertical columns, called groups, numbered from 1 to 18 (older periodic tables use a system based on roman numerals). Groups 1, 2, and 13–18 are the main group elements, listed as A in older tables. Groups 3–12 are in the middle of the periodic table and are the transition elements, listed as B in older tables. The two rows of 14 elements at the bottom of the periodic table are the lanthanides and the actinides, whose positions in the periodic table are indicated in group 3.
Metals, Nonmetals, and Semimetals
The heavy orange zigzag line running diagonally from the upper left to the lower right through groups 13–16 in Figure \(\PageIndex{1}\) divides the elements into metals (in blue, below and to the left of the line) and nonmetals (in bronze, above and to the right of the line). Gold-colored lements that lie along the diagonal line exhibit properties intermediate between metals and nonmetals; they are called semimetals.
The distinction between metals and nonmetals is one of the most fundamental in chemistry. Metals—such as copper or gold—are good conductors of electricity and heat; they can be pulled into wires because they are ductile; they can be hammered or pressed into thin sheets or foils because they are malleable; and most have a shiny appearance, so they are lustrous. The vast majority of the known elements are metals. Of the metals, only mercury is a liquid at room temperature and pressure; all the rest are solids.
Nonmetals, in contrast, are generally poor conductors of heat and electricity and are not lustrous. Nonmetals can be gases (such as chlorine), liquids (such as bromine), or solids (such as iodine) at room temperature and pressure. Most solid nonmetals are brittle, so they break into small pieces when hit with a hammer or pulled into a wire. As expected, semimetals exhibit properties intermediate between metals and nonmetals.
Example \(\PageIndex{1}\)
Based on its position in the periodic table, do you expect selenium to be a metal, a nonmetal, or a semimetal?
Given: element
Asked for: classification
Strategy:
Find selenium in the periodic table shown in Figure \(\PageIndex{1}\) and then classify the element according to its location.
Solution:
The atomic number of selenium is 34, which places it in period 4 and group 16. In Figure \(\PageIndex{1}\), selenium lies above and to the right of the diagonal line marking the boundary between metals and nonmetals, so it should be a nonmetal. Note, however, that because selenium is close to the metal-nonmetal dividing line, it would not be surprising if selenium were similar to a semimetal in some of its properties.
Exercise \(\PageIndex{1}\)
Based on its location in the periodic table, do you expect indium to be a nonmetal, a metal, or a semimetal?
Answer: metal
Descriptive Names
As previously noted, the periodic table is arranged so that elements with similar chemical behaviors are in the same group. Chemists often make general statements about the properties of the elements in a group using descriptive names with historical origins. For example, the elements of Group 1 are known as the alkali metals, Group 2 are the alkaline earth metals, Group 17 are the halogens, and Group 18 are the noble gases.
Group 1: The Alkali Metals
The alkali metals are lithium, sodium, potassium, rubidium, cesium, and francium. Hydrogen is unique in that it is generally placed in Group 1, but it is not a metal.
The compounds of the alkali metals are common in nature and daily life. One example is table salt (sodium chloride); lithium compounds are used in greases, in batteries, and as drugs to treat patients who exhibit manic-depressive, or bipolar, behavior. Although lithium, rubidium, and cesium are relatively rare in nature, and francium is so unstable and highly radioactive that it exists in only trace amounts, sodium and potassium are the seventh and eighth most abundant elements in Earth’s crust, respectively.
Group 2: The Alkaline Earth Metals
The alkaline earth metals are beryllium, magnesium, calcium, strontium, barium, and radium. Beryllium, strontium, and barium are rare, and radium is unstable and highly radioactive. In contrast, calcium and magnesium are the fifth and sixth most abundant elements on Earth, respectively; they are found in huge deposits of limestone and other minerals.
Group 17: The Halogens
The halogens are fluorine, chlorine, bromine, iodine, and astatine. The name halogen is derived from the Greek words for “salt forming,” which reflects that all the halogens react readily with metals to form compounds, such as sodium chloride and calcium chloride (used in some areas as road salt).
Compounds that contain the fluoride ion are added to toothpaste and the water supply to prevent dental cavities. Fluorine is also found in Teflon coatings on kitchen utensils. Although chlorofluorocarbon propellants and refrigerants are believed to lead to the depletion of Earth’s ozone layer and contain both fluorine and chlorine, the latter is responsible for the adverse effect on the ozone layer. Bromine and iodine are less abundant than chlorine, and astatine is so radioactive that it exists in only negligible amounts in nature.
Group 18: The Noble Gases
The noble gases are helium, neon, argon, krypton, xenon, and radon. Because the noble gases are composed of only single atoms, they are called monatomic. At room temperature and pressure, they are unreactive gases. Because of their lack of reactivity, for many years they were called inert gases or rare gases. However, the first chemical compounds containing the noble gases were prepared in 1962. Although the noble gases are relatively minor constituents of the atmosphere, natural gas contains substantial amounts of helium. Because of its low reactivity, argon is often used as an unreactive (inert) atmosphere for welding and in light bulbs. The red light emitted by neon in a gas discharge tube is used in neon lights.
Note
The noble gases are unreactive at room temperature and pressure.
Periodic Law in the Periodic Table: https://youtu.be/ciJYvhRF5i4
Summary
- The periodic table is used as a predictive tool.
The periodic table is an arrangement of the elements in order of increasing atomic number. Elements that exhibit similar chemistry appear in vertical columns called groups (numbered 1–18 from left to right); the seven horizontal rows are called periods. Some of the groups have widely-used common names, including the alkali metals (Group 1) and the alkaline earth metals (Group 2) on the far left, and the halogens (Group 17) and the noble gases (Group 18) on the far right. The elements can be broadly divided into metals, nonmetals, and semimetals. Semimetals exhibit properties intermediate between those of metals and nonmetals. Metals are located on the left of the periodic table, and nonmetals are located on the upper right. They are separated by a diagonal band of semimetals. Metals are lustrous, good conductors of electricity, and readily shaped (they are ductile and malleable), whereas solid nonmetals are generally brittle and poor electrical conductors. Other important groupings of elements in the periodic table are the main group elements, the transition metals, the lanthanides, and the actinides.
FAQs
2.6: Introduction to the Periodic Table? ›
The periodic table is an arrangement of the elements in order of increasing atomic number. Elements that exhibit similar chemistry appear in vertical columns called groups (numbered 1–18 from left to right); the seven horizontal rows are called periods.
What is the introduction of periodic table? ›The periodic table is a tabular array of the chemical elements organized by atomic number, from the element with the lowest atomic number, hydrogen, to the element with the highest atomic number, oganesson. The atomic number of an element is the number of protons in the nucleus of an atom of that element.
How do you introduce the periodic table to students? ›Create a knowledge bank on the board with key words and facts about elements in the periodic table. Ask the students to get into groups to create a song about the periodic table. Their composition must include at least four facts and 10 key words from the knowledge bank.
What element is 2.8 1? ›The electronic configuration of sodium (2.8. 1) shows that sodium, Na: is in period 3.
How do you introduce the periodic table to a child? ›- Try a merka Learning Kit. ...
- Go Over It Each Day (in Song) ...
- Play an Educational App. ...
- Use Fun Fact Flash Cards. ...
- Build Your Own with Post-It Notes.
| Atomic Number | Element | Symbol |
|---|---|---|
| 1 | Hydrogen | H |
| 2 | Helium | He |
| 3 | Lithium | Li |
| 4 | Beryllium | Be |
Scientists can use the table to analyze reactivity among elements, predict chemical reactions, understand trends in periodic properties among different elements and speculate on the properties of those yet to be discovered. The modern periodic table arranges the elements by their atomic numbers and periodic properties.
What is the 2 8 8 18 rule in chemistry? ›It is an arrangement of electrons in various shells, sub-shells and orbitals in an atom. It is written as 2, 8, 8, 18, 18, 32. It is written as nlx ( where n indicates the principal quantum number), l indicates the azimuthal quantum number or sub-shell, and x is the number of electrons.
What is 2.8 8.2 on the periodic table? ›The electron arrangement of carbon is 2.8. 8.2.
At what age should I learn the periodic table? ›At 14–16, students will learn about patterns of reactivity and will use the periodic table to determine the number of shells and electrons in an atom. As they progress in their studies, they will also look at periodicity and find many more patterns.
At what age should you memorize the periodic table? ›
You can begin as early as 5 years-old, but older kids would enjoy it as well. Then, when they are older and need to take it in high school, they will not fear it so much because they will already be familiar with many of the ideas.
In what order should I learn periodic table? ›It's easiest to learn the element symbols that go with the names, write in the symbols, and then add the names. Start small, with one or two rows or columns at a time. Whenever you get a chance, write out what you know, and then add to it.
How do you memorize the first 20 elements? ›- Happy Henry Lives Beside Boron Cottage, Near Our Friend Nelly Nancy Mg Allen. Silly Patrick Stays Close. Arthur Kisses Carrie.
- Here He Lies Beneath Bed Clothes, Nothing On, Feeling Nervous, Naughty Margret Always Sighs, ” Please Stop Clowning Around ” (18 elements)
Today, with 118 known elements, it is widely regarded as one of the most significant achievements in science.
What is the summary of the periodic table of elements? ›The periodic table separates elements into metals, nonmetals, and semimetals. The periodic table is also separated into main group elements, transition metals, lanthanide elements, and actinide elements. The lanthanide and actinide elements are also referred to as inner transition metal elements.
Has element 119 been made? ›It is the lightest element that has not yet been synthesized.
What is the basic structure of the periodic table? ›The basic structure of the periodic table is the tabular form consisting of vertical columns and horizontal rows in which the elements are arranged on the basis of ascending order of the atomic numbers of the elements. Thus, this table is also based on the periodicity or recurrence of the properties of the elements.
Is it important to learn periodic table? ›Memorizing the periodic table is important because it is organized and gives a lot of information about elements. Also, it makes students understand how elements relate to one another.
How do you memorize the first 30 elements? ›If we are talking about the first 30 elements then the periodic table starts with Hydrogen and ends at Zinc that is an element with atomic number 30. These elements can be remembered by this line: Harley Health Like Beautiful Body of Cheetah Name Opposite Falcon Nest.
How many groups are there in the periodic table? ›The s-, p-, and d-block elements of the periodic table are arranged into 18 numbered columns, or groups.
How much periodic table should I learn? ›
Answer: You should learn the elements till 30 in order. 1, 2, 13, 14, 15, 16, 17 and 18.
Why is it so hard to learn the periodic table? ›It's Complex. The periodic table contains only the symbol of elements. The symbols of most elements do start with their names, however, in some cases, the symbols are based on their Latin words. For instance, Iron is abbreviated as Fe, which is based on its Latin name Ferrum.
Why do schools teach periodic table? ›To summarize, the periodic table is important because it is organized to provide a great deal of information about elements and how they relate to one another in one easy-to-use reference. The table can be used to predict the properties of elements, even those that have not yet been discovered.
What are the three rules in chemistry? ›When assigning electrons to orbitals, we must follow a set of three rules: the Aufbau Principle, the Pauli-Exclusion Principle, and Hund's Rule.
Why do shells start with K? ›The first shell Is called K shell because: The electron shells were named by Spectroscopist Charles G Barkla. He named the innermost shell as K shell as he noticed that the X-rays emit two types of energies. He further named those two energies as type A, higher energy and type B, lower energy X-ray.
Why is 3rd shell 8 or 18? ›Q. second and third periods can accommodate 8 and 18 electrons respectively. Since their outermost shells can contain only 8 electrons, there are only 8 elements in boththe periods.
What is the 36 electron rule? ›Effective Atomic Number rule: Effective Atomic Number = atomic number of a metal + (Number of ligands x electrons donated by each ligand) – positive charge on the metal. Hence, the effective atomic number of this compound is 36, which is equal to the atomic number of krypton(36).
What is the magic number 2 8 8 18? ›The numbers 2, 8, 8, 18, 18, 32 are known as magic numbers. It is because of the fact that the elements which occur after these intervals have similar properties. For example, atomic number of Li is 3.
What elements break the octet rule? ›What elements can be an exception to the octet rule? There aren't enough electrons in hydrogen, beryllium, or boron to make an octet. There is only one valence electron in hydrogen, and there is only one site for it to make a connection with another atom.
What is 2.8 6 on the periodic table? ›Electronic Configuration of the element is 2, 8, 6 . The element is Sulphur.
What element is 2.8 7? ›
-So, the number of electrons present in an atom = 2+8+7 = 17. -Therefore the atomic number of the element is equal to 17. -The element having atomic number 17 is Chlorine.
What grade level is the periodic table taught? ›In 6th through 8th grades, students learn about the basics of chemistry, including atoms, elements, compounds, and the periodic table of elements. During this time, they will learn about the atomic structure and what makes up different atoms.
What grade level is periodic table? ›In many school districts, the periodic table is first taught as part of fifth-grade science. This is primarily an introduction to the periodic table and the elements, which students study in more depth in later grades.
Do schools make you memorize the periodic table? ›Most students do not have to memorize the whole thing, just the most common elements in chemistry. Some teachers test on these elements to see if the student can tell the properties of them and remember the abbreviations.
Do doctors have to memorize the periodic table? ›There is no reason whatever for a medical student to memorise the Periodic Table of the elements. There are many many things you need to learn as a medical student, but learning the Periodic Table in detail would be a waste of time and effort. Most of it will never be called upon in a medical career.
What is an element kid friendly? ›An element is a pure substance that is made from a single type of atom. Elements are the building blocks for all the rest of the matter in the world. Examples of elements include iron, oxygen, hydrogen, gold, and helium.
What is periodic table and periodicity introduction? ›In the context of chemistry and the periodic table, periodicity refers to trends or recurring variations in element properties with increasing atomic number. Periodicity is caused by regular and predictable variations in element atomic structure.
What is periodic table explanation for kids? ›In the table, the elements are placed in the order of their atomic numbers starting with the lowest number of one, hydrogen. The atomic number of an element is the same as the number of protons in that particular nucleus of an atom. In the periodic table the elements are arranged into periods and groups.
What is the introduction of the modern periodic law? ›Modern Periodic Law Definition
The modern Periodic law can be stated as: “The physical and chemical properties of the elements are periodic functions of their atomic numbers”. The atomic number is equal to the number of electrons or protons in a neutral atom.
A period is a horizontal row of the periodic table. There are seven periods in the periodic table, with each one beginning at the far left. A new period begins when a new principal energy level begins filling with electrons. Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements.
What is periodicity for dummies? ›
A pattern of repeating order is called periodicity. In the mid-1800s, Dmitri Mendeleev, a Russian chemist, noticed a repeating pattern of chemical properties in elements. Mendeleev arranged the elements in order of increasing atomic mass, to form something that resembles the modern periodic table.
Why is it called periodic table? ›It is called the periodic table because of the way the elements are arranged. You'll notice they're in rows and columns. The horizontal rows (which go from left to right) are called 'periods' and the vertical columns (going from up to down) are called 'groups'.
Who created the periodic table? ›Dmitri Mendeleev
As we have seen, Mendeleev was not the first to attempt to find order within the elements, but it is his attempt that was so successful that it now forms the basis of the modern periodic table. Mendeleev did not have the easiest of starts in life.
An element is a pure substance. It cannot be broken down into other types of substances. Each element is made up of just one type of atom.
How many elements are in the periodic table? ›Since then, the periodic table has evolved to reflect over 150 years of scientific development and understanding in chemistry and physics. Today, with 118 known elements, it is widely regarded as one of the most significant achievements in science.
How many periods and groups are there in the periodic table? ›The modern periodic table is the present form of the periodic table in which the arrangement of elements is in the increasing order of their atomic numbers. There are 18 vertical columns or groups and 7 horizontal rows or periods in the modern periodic table.
What is meant by a group in the periodic table? ›group, in chemistry, a column in the periodic table of the chemical elements. In a group, the chemical elements have atoms with identical valence electron counts and identical valence vacancy counts.