Question

1. which element reacts with oxygen to form ionic bonds?

a) calcium b) hydrogen
c) chlorine d) nitrogen

1. element x reacts with chlorine to form an ionic

compound that has the formula xcl₂. to which group on
the periodic table could element x belong?
a) group 14 b) group 2
c) group 13 d) group 15

1. molecules of hbr collide and then form h₂ and br₂.

during the collision, the bonds in the hbr molecules are
a) broken as energy is absorbed
b) broken as energy is released
c) formed as energy is absorbed
d) formed as energy is release

1. what occurs as two atoms of fluorine combine to

become a molecule of fluorine?
a) a bond is formed as energy is absorbed.
b) a bond is formed as energy is released.
c) a bond is broken as energy is absorbed.
d) a bond is broken as energy is released.

1. which of these elements has an atom with the most

stable outer electron configuration?
a) ne b) cl
c) ca d) na

1. which formula represents a molecular compound?

a) hi b) ki
c) kcl d) licl

1. describe the difference between an ionic and covalent

bond

1. describe what happens to the energy of co₂ when it

decomposes to form c and o₂ elements.

Explanation:

1. Ionic bonds form between metals and non - metals. Calcium (Ca) is a metal (Group 2), oxygen (O) is a non - metal. Calcium reacts with oxygen to form \(CaO\) (ionic compound). Hydrogen (H), chlorine (Cl), and nitrogen (N) form covalent compounds with oxygen.
2. In an ionic compound \(XCl_2\), chlorine has a charge of \(- 1\). Let the charge of \(X\) be \(x\). Using the formula \(x+2\times(-1)=0\) (since the compound is neutral), we get \(x = + 2\). Group 2 elements have a \(+2\) charge in their ionic compounds.
3. When \(HBr\) molecules collide to form \(H_2\) and \(Br_2\), the bonds in \(HBr\) (H - Br bonds) need to be broken. Bond - breaking is an endothermic process (energy is absorbed).
4. When two atoms of fluorine combine (\(F+F

ightarrow F_2\)), a bond (F - F) is formed. Bond - forming is an exothermic process (energy is released).

1. Noble gases (Group 18) have a stable outer electron configuration (full valence shell). Neon (Ne) is a noble gas. Chlorine (Cl) has \(7\) valence electrons, calcium (Ca) has \(2\) valence electrons (in its outer shell, before losing electrons), and sodium (Na) has \(1\) valence electron.
2. Molecular compounds are formed between non - metals. HI is formed between hydrogen (non - metal) and iodine (non - metal). KI, KCl, and LiCl are ionic compounds (formed between metals (K, Li) and non - metals (I, Cl)).

Answer:

1. A. calcium
2. B. Group 2
3. A. broken as energy is absorbed
4. B. A bond is formed as energy is released
5. A. Ne
6. A. HI