Which one of the following formulas of ionic compounds is the least likely to be correct? select one: a. nh4cl b. ba(oh)2 c. na2so4 d. ca2no3 e. cu(cn)2

The answer to your question is letter d. Ca₂NO₃

Explanation:

a. NH₄Cl   This formula is correct             NH₄⁺¹   +   Cl⁻¹   =  NH₄Cl

b. Ba(OH)₂  This formula is also correct   Ba⁺²     +   OH¹⁻ =  Ba(OH)₂

c. Na₂SO₄   This formula is correct           Na⁺¹     +   SO₄⁻² = Na₂SO₄

d. Ca₂NO₃   This formula is wrong            Ca⁺²    +   NO₃⁻¹ = Ca(NO₃)₂

e. Cu(CN)₂   This formula is correct          Cu⁺²     +   CN⁻¹  =  Cu(CN)₂

not clear

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.