HELP ASAP 10 POINTS Choose all the answers that apply. The elements in group 18 . 1. are highly reactive 2. are gases at room temperature 3. usually do not react with other elements 4. are in a group called the noble gases 5. are nonmetals 2, Elements with similar chemical properties are organized in the same .

group
period
electron shell
row

3. Choose all the answers that apply.

Nitrogen has an atomic number of 7. Its atomic mass is 14. Nitrogen has .

seven electrons
seven neutrons
seven electron shells
23 neutrons
14 electrons

4, Fluorine-19 is an isotope of fluorine. It has a different number of .

electrons
protons
neutrons
electron shells

5. Choose all the answers that apply.

Chromium (Cr) is a metal in group 6 and period 4. Which of the following is true?

Chromium is a noble gas.
Chromium has four electron shells.
Chromium is a good conductor of electricity.
Chromium has six electron shells.
Chromium is a solid at room temperature.

6. Which of the following statements is true?

Elements in the last period are radioactive.
Atomic weight is the same as atomic mass.
Elements in the same group have the same number of electron shells.
Atomc number equals the number of neutrons in the nucleus of an atom.

7. Sodium (Na) has 11 protons and 12 neutrons. Which of the following is the most likely atomic weight of sodium?

22.98
12.98
11.98
24.98

8. Atomic weight is the .

average number of neutrons in an element's isotopes
combined masses of an element's isotopes
weighted average of an element's isotopes

9. The atomic mass of an atom does not contain electrons because

Electrons are so small that it does not affect the mass of an atom.
Electrons are do not contain mass.
Electrons are not as important as protons and neutrons.
Electrons do not exist in all atoms.