Quiz (Atoms and atomic models and nuclear physics)

If a material has a half-life of 8 hours, how long do you have to wait until the amount of radioisotope is 1/8 its original amount?

24 hours

If a neutral element has the following chemical symbol, how many electrons does it have?

92

What is the approximate mass of a carbon atom in atomic mass units (amu)? How about a carbon monoxide molecule?

A carbon atom has a mass of about 12 amu. Carbon monoxide would then have a mass of 28 amu.

Since atoms are mostly empty space, why don't objects pass through one another?

The electrons on the atoms repel other electrons on other atoms when they get close.

Evidence for the existence of neutrons did not come until many years after the discoveries of the electron and the proton. Give a possible explanation.

The neutron lacks an electrical charge.

Why is the combination of two protons and two neutrons stable, but two protons and one neutron is not?

There are not enough neutrons to overcome the electrical repulsion of the protons.

Radioactivity is a tendency for an element or a material to

emit radiation

Helium, He, is a nonmetallic gas and the second element in the periodic table. Rather than being placed adjacent to hydrogen, H, however, helium is placed on the far right of the table because

helium is most similar to other group 18 elements.

Which of the following describes a nonmetal?

poor conductor of electricity

The mass number of an element is

sum of protons and neutrons