Question

1. what is the difference in reactivity between group 17 and group 18? why?
2. what is the atomic num 12 element magnesium?

image of mg element tile

1. in the element above of magnesium, how many protons, electrons, and neutrons does one atom have?

protons = ____ electrons = __ neutrons = ____

1. identify the following elements:

image of atomic models (one with p:6, n:6; one with electron shells)

Explanation:

Question 21

• Reactivity difference: Group 17 (halogens) is reactive; Group 18 (noble gases) is unreactive.
• Reason: Group 17 has 7 valence electrons (needs 1 to fill shell). Group 18 has a full valence shell (stable electron configuration), so no electron - gaining/losing/sharing tendency.

Question 22

In the periodic table symbol for an element, the atomic number is the number at the top (or the smaller number). For Magnesium (Mg), the atomic number is 12, which is shown as the number above the symbol in the given box.

Question 23

• Protons: The atomic number of an element is equal to the number of protons. For Magnesium, atomic number is 12, so protons = 12.
• Electrons: In a neutral atom, the number of electrons is equal to the number of protons. So electrons = 12.
• Neutrons: The number of neutrons is approximately equal to the atomic mass (rounded) minus the atomic number. The atomic mass of Magnesium is 24.305, so neutrons≈24 - 12 = 12.

Question 24

Answer:

Group 17 elements are highly reactive, while Group 18 elements (noble gases) are generally unreactive. Group 17 elements have 7 valence electrons and tend to gain 1 electron to achieve a stable octet. Group 18 elements have a full valence shell (8 electrons, except He with 2), so they have no tendency to gain, lose, or share electrons.