Question

Which electrons participate in chemical bonding?

Answer 1

core electrons

Answer 2

covalent bonds
occurs between 2 metals or two non metals

for example

h2o H is hydrogen and o is oxygen there both non metals so there call covalent bonds
if u look at the periodic table it will show u a line at the right those are non metals and rember H is non metal even if it's on the other side of the chart.