The element in Period 2 with the largest atomic radius is

• an alkaline earth metal

• a halogen

• a noble gas

• an alkali metal

Answer explanation

In Period 2, alkali metals like lithium have the largest atomic radius due to their lower nuclear charge and fewer electron shells compared to other elements in the period, making them larger than alkaline earth metals, halogens, and noble gases.

Which halogen is a liquid at STP?

• Cl₂

• F₂

• I₂

• Br₂

Answer explanation

At standard temperature and pressure (STP), bromine (Br₂) is the only halogen that exists as a liquid. Chlorine (Cl₂) and fluorine (F₂) are gases, while iodine (I₂) is a solid.

Tags

NGSS.MS-PS1-4

Which element has an atomic radius that is greater than its ionic radius?

• F

• S

• K

• O

Answer explanation

Potassium (K) has a larger atomic radius than its ionic radius because when it loses an electron to form K+, the remaining electrons are drawn closer to the nucleus, reducing the size. This is not the case for F, S, or O.

Tags

NGSS.HS-PS1-1

As the Group 1 elements of the Periodic Table are considered from top to bottom, the first ionization energy of each successive element decreases. One reason for this is that the

• nuclear charge is decreasing

• number of principal energy levels is decreasing

• number of neutrons is increasing

• distance between the valence electron and the nucleus is increasing

Answer explanation

As we move down Group 1, the number of principal energy levels increases, causing the valence electron to be further from the nucleus. This increased distance reduces the effective nuclear attraction, leading to lower ionization energy.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

What group of the Periodic Table contains the noble gases?

• 1

• 17

• 2

• 18

Answer explanation

The noble gases are found in Group 18 of the Periodic Table. This group includes elements like helium, neon, and argon, which are characterized by their lack of reactivity due to having a full valence shell.

What are two properties of most nonmetals?

• high ionization energy and poor electrical conductivity

• high ionization energy and good electrical conductivity

• low ionization energy and poor electrical conductivity

• low ionization energy and good electrical conductivity

Answer explanation

Most nonmetals have high ionization energy, meaning they hold onto their electrons tightly, and they are poor electrical conductors due to their lack of free-moving electrons. Thus, the correct choice is high ionization energy and poor electrical conductivity.

Tags

NGSS.HS-PS1-1

Compared to atoms of metals, atoms of nonmetals generally have

• lower electronegativities and higher ionization energies

• higher electronegativities and lower ionization energies

• lower electronegativities and lower ionization energies

• higher electronegativities and higher ionization energies

Answer explanation

Nonmetals typically have higher electronegativities, meaning they attract electrons more strongly, and higher ionization energies, indicating they require more energy to remove an electron compared to metals.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

On the Periodic Table, an element classified as a semimetal (metalloid) can be found in

• Period 6, Group 15

• Period 4, Group 15

• Period 3, Group 16

• Period 2, Group 14

Answer explanation

The correct choice is Period 3, Group 16, where the element is silicon (Si), a well-known semimetal. Other options do not contain semimetals, as they either belong to different groups or periods.

Tags

NGSS.HS-PS1-1

What is the electron configuration of an atom of a Period 3 element?

• 2-1

• 2-3

• 2-8-1

• 2-8-9-2

Answer explanation

The electron configuration of a Period 3 element, such as sodium, is 2-8-1. This indicates 2 electrons in the first shell, 8 in the second, and 1 in the third, making 2-8-1 the correct choice.

Tags

NGSS.HS-PS1-1

Which period contains the greatest number of metals?

• 1

• 3

• 2

• 4

Answer explanation

Period 4 contains the greatest number of metals, including transition metals and post-transition metals, making it richer in metallic elements compared to periods 1, 2, and 3.