Give the number of valence electrons in the following elements and identify the element’s reactivity (chemically stable or unstable). 1) magnesium, mg 2) cesium, cs 3) neon, ne 4) carbon, c 5) krypton, kr example response for one element: calcium, ca has 2 valence electrons and is chemically unstable.

Element  Valence electrons   Stability

1)  Mg                    2                  Unstable

2) Cs                      1                  Highly unstable

3) Ne                     8                  Stable

4) C                        4                  Stable

5) Kr                       8                  Stable

Explanation:

Elements with eight valence electrons (the noble gases) are stable because they already have a complete valence shell.

Elements with one valence electron (the alkali metals) are highly unstable because they can easily lose one electron to reach a stable configuration.

Elements with two valence electrons (the alkaline earth metals) are unstable because they need to lose only two electrons to reach a stable configuration.

Carbon would have to either lose or gain four valence electrons to form an ionic compound. Instead, the atoms join to form stable ring systems with covalent bonds.