An element has 1 electron in its outer shell and is highly reactive. Which group does it most likely belong to?

• Group 2

• Group 17

• Group 18

• Group 1

Answer explanation

The element with 1 electron in its outer shell is likely an alkali metal, which belongs to Group 1. These elements are highly reactive due to their tendency to lose that single electron easily.

Why are elements in the same group on the Periodic Table often similar?

• They have the same atomic mass

• They have the same number of neutrons

• They have similar numbers of outer electrons

• They have identical atomic numbers

Answer explanation

Elements in the same group have similar chemical properties because they possess similar numbers of outer electrons. This similarity in electron configuration leads to comparable reactivity and bonding behavior.

Which element would be most reactive in Group 1?

• Lithium (Li)

• Sodium (Na)

• Potassium (K)

• Francium (Fr)

Answer explanation

Francium (Fr) is the most reactive element in Group 1 due to its larger atomic size and lower ionization energy compared to other alkali metals, making it more likely to lose its outer electron and react.

Which element is least likely to form chemical bonds?

• Oxygen

• Fluorine

• Argon

• Nitrogen

Answer explanation

Argon is a noble gas with a full valence shell, making it chemically inert and least likely to form bonds. In contrast, oxygen, fluorine, and nitrogen are more reactive due to their incomplete valence shells.

Why are noble gases found in Group 18?

• They are highly reactive metals

• They have full outer electron shells

• They bond easily with other elements

• They all have the same mass

Answer explanation

Noble gases are found in Group 18 because they have full outer electron shells, making them stable and largely unreactive. This stability is why they do not easily bond with other elements.

Which of the following is true about elements in the same period?

• They have similar reactivity

• They are all nonmetals

• They have the same number of electron shells

• They all have the same density

Answer explanation

Elements in the same period have the same number of electron shells, which is why they share this characteristic. The other options are incorrect as reactivity, nonmetal status, and density vary across a period.

A student finds an element in Group 17. What is most likely true about it?

• It is a noble gas

• It is a very stable element

• It reacts easily with Group 1 elements

• It is located in Period 1

Answer explanation

Group 17 elements, known as halogens, are highly reactive, especially with Group 1 alkali metals. They readily form compounds with these elements, unlike noble gases which are stable and unreactive.

Tags

NGSS.MS-PS1-2

What pattern is observed as you move left to right across a period?

• Atomic mass decreases

• Reactivity increases for metals

• Elements become less metallic

• Atomic number remains constant

Answer explanation

As you move left to right across a period in the periodic table, elements become less metallic. This trend reflects the increasing electronegativity and ionization energy, leading to nonmetals dominating the right side.

Why does reactivity decrease for metals from left to right across a period?

• A. Metals gain more protons

• B. Outer electrons are more easily lost

• C. Atoms hold onto electrons more tightly

• D. Neutrons increase in number

Answer explanation

Reactivity decreases across a period because atoms hold onto their outer electrons more tightly due to increased nuclear charge. This makes it harder for metals to lose electrons, reducing their reactivity.

Which trend occurs as you move down a group of metals?

• Reactivity decreases

• Atomic number decreases

• Atomic radius increases

• Elements become gases

Answer explanation

As you move down a group of metals, the atomic radius increases due to the addition of electron shells, which outweighs the increase in nuclear charge. This trend is consistent across the periodic table.