Pupil sheet · Covalent molecules
Covalent molecules — return questions
Name ______________________ Date ____________
Use one to two weeks after the lessons. Keep the notes and the lesson closed.
1. state / explain / deduce / identify / name
(a) State what a covalent bond is. Hydrogen bromide, HBr, is made of molecules; a bromine atom has 7 outer electrons. Explain why a hydrogen atom and a bromine atom share one pair of electrons, not two. (b) Supplement: in a molecule X2, the two atoms share two pairs of electrons and each atom keeps two lone pairs. Deduce how many outer electrons an atom of X has, identify X from carbon, nitrogen, oxygen and fluorine, and name the type of bond.
(a) The covalent bond, and hydrogen bromide
(b) Supplement: the molecule X2
2. describe / predict / explain
Hydrogen chloride, HCl, boils at −85 °C. (a) Describe, in terms of structure and bonding, why hydrogen chloride is a gas at room temperature, and why liquid hydrogen chloride does not conduct electricity. (b) Supplement: hydrogen sulfide, H2S, is also a simple molecular substance, and its molecules attract each other more strongly than HCl molecules do. Predict whether hydrogen sulfide boils above or below −85 °C, and explain your prediction in terms of energy.
(a) Gas at room temperature, and no conductivity
(b) Supplement: hydrogen sulfide