From left to right across each row, elements are arranged by increasing atomic mass. They are sometimes called families, because elements within a group are similar but not identical to one another, like people in a family. Mendeleev’s table of the elements organizes the elements by atomic mass.

In the modern periodic table, elements are arranged by increasing atomic number (number of protons). Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.

The elements on the modern periodic table are arranged in the increasing order of their atomic number and repeating properties.

Mendeleev

Dmitri Mendeleev

Other “Father of Chemistry” Scientists

The modern periodic table is used to organize all the known elements. Elements are arranged in the table by increasing atomic number. In the modern periodic table, each element is represented by its chemical symbol. Elements in the same group have similar properties.

118 Elements and Their Symbols and Atomic Numbers

Terms in this set (10)

• Hydrogen. H.
• Helium. He.
• Lithium. Li.
• Beryllium. Be.
• Boron. B.
• Carbon. C.
• Nitrogen. N.
• Oxygen. O.

The first 30 elements of the periodic table and their symbols

In order of increasing atomic number, the first 20 elements and their symbols are:

• Hydrogen (H)
• Helium (He)
• Lithium (Li)
• Beryllium (Be)
• Boron (B)
• Carbon (C)
• Nitrogen (N)
• Oxygen (O)

First 40 Chemical Elements & Their Symbols

Valency of First 30 Elements

The Elements, sorted by Atomic Number

Gold is a metallic element and a transition element having a formula Au. It has the valency of 3 or 1.

This is a table of the valences of the elements. Valence is also known as oxidation state….Table of Valences of the Elements 6.

Au

The valency of oxygen is 2, because it needs two atoms of hydrogen to form water. Ammonia which is NH 3 , One atom of nitrogen combines with 3 atoms of hydrogen.

If its Valence electrons are less than 4, then valency is equal to number of valence electrons and if it is more than 4 then valency is obtained by subtracting number of valence electrons from 8. Atomic Number of oxygen is 8. So, electronic Configuration of oxygen= 2, 6

six valence electrons

So… for the element of OXYGEN, you already know that the atomic number tells you the number of electrons. That means there are 8 electrons in an oxygen atom. Looking at the picture, you can see there are two electrons in shell one and six in shell two. ► More about the history and places to find oxygen.

8 electrons

Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.

The names of the electron shell were given by a spectroscopist named Charles G Barkla. He named the innermost shell has k shell because he noticed that the X-rays emitted two types energies. He noticed that K type X-rays emitted the highest energy. Therefore, he named the innermost shell as the K shell.

The electron capacity of the third shell is 8, when there are no shells above it. And that is the case for all elements in the third period. It is only when there are outer shells surrounding it that the third (or higher) shell has a higher capacity.

Thus, the electron shells of an atom are populated from the inside out, with electrons filling up the low-energy shells closer to the nucleus before they move into the higher-energy shells further out. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.