Question

1 to 20 elements with their atomic no. mass and valency​

Answer 1

Answer:

The periodic table is the tabular arrangement of all the chemical elements on the basis of their respective atomic numbers. In the periodic table, the vertical columns are called ‘groups’ and the horizontal rows are called ‘periods’. The modern periodic table is based on the modern periodic law put forward by the English physicist Henry Moseley, which states that “the properties of elements are periodic functions of their atomic numbers”. Periodic trends in the properties of the elements can be observed down the groups and across the periods of the modern periodic table.

Every chemical element has a specific atomic number, which provides insight into the number of protons present within its nucleus. All isotopes of an element fall under a single cell on the periodic table, since they all share the same atomic number.

Answer 2

$\textsf{Atomic number - Element - Atomic mass - Valency}$

1 - Hydrogen - 1.008 - 1

2 - Helium - 4.00 - 0

3 - Lithium - 6.94 - 1

4 - Beryllium - 9.01 - 2

5 - Boron - 10.81 - 3

6 - Carbon - 12.01 - 4

7 - Nitrogen - 14.01 - 3

8 - Oxygen - 16.00 - 2

9 - Fluorine - 19.00 - 1

10 - Neon - 20.18 - 0

11 - Sodium - 22.99 - 1

12 - Magnesium - 24.31 - 2

13 - Aluminium - 26.98 - 3

14 - Silicon - 28.09 - 4

15 - Phosphorus - 30.97 - 3

16 - Sulphur - 32.07 - 2

17 - Chlorine - 35.45 - 1

18 - Argon - 39.95 - 0

19 - Potassium - 39.10 - 1

20 - Calcium - 40.08 - 2