Chemistry chapter 2

The smallest particle of an element that can be identified as that element is

an atom

_{Which of the following consists of several atoms?}

a molecule

_{Which one of the following is electrically neutral?}

a neutron

_{Which subatomic particle contributes least to the mass of the atom?}

electron

_{Two atoms must represent the same element if they both have the same:}

atomic number

_{Mercury-202 has how many neutrons in its nucleus?}

122

_{Uranium-235 has how many protons in the nucleus?}

92

_{Cobalt has atomic number 27. Cobalt-60 is used in the medical treatment of cancer. How many neutrons and protons are contained in the nucleus of this isotope?}

33 neutrons and 27 protons

_{The quantity (mass number - atomic number) provides:}

the number of neutrons in a nucleus

_{The mass number is:}

the sum of protons + neutrons

_{List the number of electrons, protons, and neutrons are in a neutral atom of Ba-138?}

_{56 electrons, 56 protons, 82 neutrons}

_{A hypothetical element contains three isotopes of mass 16.0 amu, 17.0 amu, and 18.0 amu with relative abundances of 20.0%, 50.0% and 30.0%, respectively. The average atomic mass is:}

_{17.1 amu}

_{The element rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 (185Re) has in its nucleus:}

_{75 protons, 110 neutrons}

_{Which of the following represents a pair of isotopes?}

H₁¹ H₁²

_{Which one of the following elements is not matched with the correct atomic mass?}

_{Ba, 56 amu}

_{The form of radioactivity that penetrates matter most easily is:}

_{gamma rays}

_{The form of radiation that has no mass and no charge consists of:}

_{gamma rays}

_{What protective shielding is sufficient for gamma rays?}

 _{Lead sheet}

_{What protective shielding is sufficient for beta particles?}

_{Aluminum sheet and lead sheet both provide protection.}

_{What protective shielding is sufficient for alpha particles?}

_{Paper, aluminum sheet and lead sheet all provide protection.}

_{The amount of a radioisotope that remains after two half-lives have passed is:}

25%