Identify each of the following elements: a. a member of the same family as oxygen whose most sta‐ ble ion contains 54 electrons b. a member of the alkali metal family whose most stable ion contains 36 electrons c. a noble gas with 18 protons in the nucleus d. a halogen with 85 protons and 85 electrons

a. Tellurium

b. Rubidium

c. Argon

d. Astatine

Explanation:

a. An element of the same family as oxygen corresponds to group 16 or 6A, its most stable ion is -2, therefore if the ion has 54 electrons the neutral element should have 52 electrons and also 52 protons. Tellurium

b. The ions from alkali metals are +1, therefore the neutral elements have 1 more electron and proton, since the ion has 36 electrons the neutral element has 37. Rubidium

c. This is direct, look for the element with Z = 18. Argon

d. This is also direct, look for the element with Z = 85. Astatine

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