Chemistry

1Element Y has electron configuration 2, 8, 7. It forms ions with charge

2Across a period, first ionisation energy generally

3The electron configuration of calcium (Z = 20) is

4An ion X²⁻ has 18 electrons. The atomic number of X is

5Elements in the same group of the periodic table have the same number of

6An element has isotopes of mass 63 (69%) and 65 (31%). Its relative atomic mass is about

7Which of the following elements is an alkali metal?

8An element X has electron configuration 2, 8, 2. X belongs to

9The electron configuration 1s² 2s² 2p⁶ 3s² 3p⁵ belongs to

10Elements in the same group have the same number of