Practice: Atomic Mass - Henriksen Science



Practice: Atomic Mass

_____1. Define mass number

a) Number of electrons in the atom.

b) Number of protons and neutrons in the atom.

c) Number of protons in the atom.

d) Average mass per atom for a random sample of the element.

_____2. An atom of strontium-88 contains: (a) 44 protons and 44 neutrons;

(b) 38 protons and 38 neutrons; (c) 50 protons and 38 neutrons;

(d) 38 protons and 50 neutrons.

_____3. Define atomic weight.

a) Number of electrons in the atom.

b) Number of protons and neutrons in the atom.

c) Number of protons in the atom.

d) Average mass per atom for a random sample of the element.

_____4. The average atomic mass (or atomic weight) of an element represents the (a) the number of protons; (b) the mass number of the isotope; (c) the average weight of all the isotopes;

(d) the number of protons + the number of neutrons.

_____5. An element has 2 stable isotopes. One isotope has a mass number of 64, and the other has a mass number of 67. Which one of the following could be the atomic weight of this element? (a) 64 ; (b) 67 ; (c) 131 ; (d) 65.4 ; (e) 67.2.

**Justify (explain, defend) your answer to #5.

6. The mass number of the isotopes of an element (instead of the actual mass in atomic mass units) can be used to calculate an approximate atomic mass. A sample of an element, as it occurs naturally, has the following composition:

78.6% of the atoms of the element have a mass number of 24

10.1% of the atoms of the element have a mass number of 25

11.3% of the atoms of the element have a mass number of 26.

Calculate the average atomic mass of the element. Show your work and report your final answer with 1 decimal point.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download