1 .A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____. (Concept 2.1) molecule element compound isotope proton 2 .Which of the following is a trace element required by most living organisms? (Concept 2.1) oxygen magnesium nitrogen carbon hydrogen 3 .Which of the following subatomic particles always has a positive charge? (Concept 2.2) proton neutron electron atom element 4 .Changing the number of _____ would change an atom into an atom of a different element. (Concept 2.2) bonds formed by an atom electrons circling the nucleus of an atom protons in an atom particles in the nucleus of an atom neutrons in an atom 5 .The atoms of different phosphorus isotopes _____. (Concept 2.2) have different atomic numbers have different numbers of neutrons react differently with other atoms have different numbers of electrons have different numbers of protons 6 .How an atom chemically behaves when it comes into contact with other atoms is determined by its _____. (Concept 2.2) nucleus size; smaller things are chemically more reactive protons neutrons electron configuration 7 .Which of the following holds atoms together in a molecule? (Concept 2.3) ionic bonds between atoms the transfer of protons from one atom to another the sharing of electrons between atoms the loss of neutrons by atoms the sharing of protons between atoms 8 .Hydrogen bonding is most often seen _____.