Question

Write the symbol for the elements that fit the following descriptions

1. 10 electrons in each -3 ion
2. 18 electrons in each +2 ion
3. The alkaline earth metal in the third period

Answer 1

1. -3 means 3 "extra" electrons
... this element is atomic number 7

2. +2 means 2 "lost" electrons
... this element is atomic number 20

3. column 2, row 3