quiz 8

Which of the following sets of coefficients balance the following chemical equation? ___ N2 + ___ H2 ___ NH3

1, 3, 2

How much is left of a 1600 g sample of a radioactive isotope after 10 days if its half-life is 2.5 days?

100g

How many protons are there in an atom of Na28/11?

11

How many neutrons are there in an atom of 39K19 ?

20

When the number of protons in the nucleus exceeds _______, the nucleus is unstable to radioactive decay.

82

The smallest amount of a fissionable material that will allow a self-sustaining chain reaction is called the

Critical mass.

The proper name for the chemical compound N20 is

Dinitrogen oxide

Atoms forming a covalent bond are held together by the

Electrical attraction two nuclei have for the shared electrons

Alpha particles are

Energetic helium nuclei

The mass of a helium atom with two protons and two neutrons in its nucleus is

Greater than the sum of the masses of two hydrogen atoms and two neutrons.

The octet rule of chemical binding applies to the formation of

Ionic and covalent bonds.

Covalent and ionic bonds differ in that

Ionic bonds don't involve the sharing of electrons

The atomic number of an element is equal to the number of _________ in one of its atoms.

Protons

The most important force between a proton and a neutron is the __________ force.

Strong nuclear

When they participate in chemical reactions, atoms in columns IA and IIA of the periodic table

Tend to lose electrons and become positive ions

Salts are made of elements found on opposite sided of the periodic table because element on

The right tend to form negative ions while those on the left tend to form positive ions

What is the symbol for the element whose atoms have 40 electrons each?

Zr

9. What elements tend to form ionic compounds?

lements found on opposite sides of the periodic table

In metallic bonds, the valence electrons

mostly free to move about

In a nucleus, the mass number equals the number of

nucleons

When hydrogen (electronegativity = 2.1) bonds with oxygen (electronegativity = 3.5) to form water, what is the polarity of the hydrogen-oxygen bond?

polar-covalent