Question

Choose all the answers that apply. The elements in group 18 _____.

are highly reactive

are gases at room temperature

usually do not react with other elements

are in a group called the noble gases

are nonmetals

Elements with similar chemical properties are organized in the same _____.
a) group
b) period
c) electron shell
d) row

Choose all the answers that apply.
Nitrogen has an atomic number of 7. Its atomic mass is 14. Nitrogen has _____.
a) seven electrons
b) seven neutrons
c) seven electron shells
d) 23 neutrons
e) 14 electrons

Fluorine-19 is an isotope of fluorine. It has a different number of _____.
a) electrons
b) protons
c) neutrons
d) electron shells

Choose all the answers that apply.
Chromium (Cr) is a metal in group 6 and period 4. Which of the following is true?
a) Chromium is a noble gas.
b) Chromium has four electron shells.
c) Chromium is a good conductor of electricity.
d) Chromium has six electron shells.
e) Chromium is a solid at room temperature.

Which of the following statements is true?
a) Elements in the last period are radioactive.
b) Atomic weight is the same as atomic mass.
c) Elements in the same group have the same number of electron shells.
d) Atomic number equals the number of neutrons in the nucleus of an atom.

Sodium (Na) has 11 protons and 12 neutrons. What is the most likely atomic weight of sodium?
a) 22.98
b) 12.98
c) 11.98
d) 24.98

Answer 1

The elements in group 18 are the noble gases, which are typically unreactive and are gases at room temperature. Nitrogen has seven electrons and seven neutrons, while Fluorine-19 has nine protons and ten neutrons. Chromium is a metal with four electron shells, and sodium's most likely atomic weight is 22.98.

Step-by-step explanation:

The elements in group 18 are known as the noble gases. They are generally unreactive due to their full valence electron shells, making them less likely to participate in chemical reactions. These elements include helium, neon, argon, krypton, xenon, and radon, and they exist as gases at room temperature. Elements in the periodic table that have similar chemical properties are organized in the same group.

Nitrogen, with an atomic number of 7 and an atomic mass of 14, has seven electrons and seven neutrons. Fluorine-19 is an isotope of fluorine that has a different number of neutrons compared to other fluorine isotopes. The isotope designation of 19 implies that the atomic mass of fluorine in this case is 19, which means that since fluorine has 9 protons, it must also have 10 neutrons (19 - 9 = 10).

Chromium (Cr), which is a metal in group 6 and period 4, has four electron shells, is a good conductor of electricity and is a solid at room temperature. It is not a noble gas and does not have six electron shells.

Elements in the same group have the same number of valence electrons, not necessarily the same number of electron shells. Atomic weight and atomic mass are often used interchangeably, but they are technically not the same; atomic weight is the average mass of an atom of an element, taking into account the abundance of its naturally occurring isotopes, while atomic mass is the mass of a specific isotope.

The most likely atomic weight of sodium, which has 11 protons and 12 neutrons, is 22.98, as it is the closest whole number to the sum of its protons and neutrons (11 + 12 = 23).