Chemistry-Average Atomic Mass and Subatomic Particles

1. Chlorine-35, which has an amu of 34.969 and a natural abundance of 75.77%

2. Chlorine-37, which has an amu of 36.966 and a natural abundance of 24.23% What is the average atomic mass of chlorine?

35.15 amu

amu	Natural Abundance
31.972	95.002
32.971	0.76
33.967	4.22
35.967	0.014

What is the average atomic mass of sulfur?

32.06 amu

If the abundance of ⁸⁵Rb is 72.17% (amu 84.9118) and the abundance of ⁸⁷Rb is 27.83% (amu 86.9092), what is the average atomic mass of rubidium? Report the answer to 2 places past the decimal.

85.47 amu

1. If the abundance of ²³⁴U is 0.0055%, the abundance of ²³⁵U is 0.7200%, and the abundance of ²³⁸U is 99.2745%, what is the average atomic mass of uranium? The atomic masses of the isotopes are 234.0409 amu, 235.0439 amu and 238.0508 amu respectively. Report the answer to 2 places past the decimal.

238.03 amu

1. If the abundance of ²³⁴U is 0.0055%, the abundance of ²³⁵U is 0.7200%, and the abundance of ²³⁸U is 99.2745%, what is the average atomic mass of uranium? The atomic masses of the isotopes are 234.0409 amu, 235.0439 amu and 238.0508 amu respectively. Report the answer to 2 places past the decimal.

47.92 amu

1. Why is the average atomic mass in amu of Carbon reported as 12.011 in the periodic table of the elements?

Because it is a weighted average of all the isotopes of Carbon.

1. ⁶³Cu and ⁶⁵Cu. ⁶³Cu has an atomic mass of 62.9298 amu and an abundance of 69.09%. The other isotope, ⁶⁵Cu, has an abundance of 30.91%. The average atomic mass between these two isotopes is 63.546 amu. Calculate the actual atomic mass of ⁶⁵Cu.

64.92 amu

1. The percent abundance of these isotopes is as follows: ²⁴Mg (78.70%), ²⁵Mg (10.13%), and ²⁶Mg (11.7%). The average atomic mass of the three isotopes is 24.3050 amu. If the atomic mass of ²⁵Mg is 24.98584 amu, and ²⁶Mg is 25.98259 amu, calculate the actual atomic mass of ²⁴Mg.

24.3050

Complete the table:

Isotope	Mass (amu)	Relative Abundance (%)
Neon-20	19.992		90.51
Neon-21	20.994
Neon-22			9.22
	Avg. Atomic Mass =	Total %:

Neon-21 Abundance: .27%

Average Atomic Mass of Neon: 20.18 amu

Neon-22: 22.00 amu

What things are always equal to each other? And assume that it is a neutral atom?

Atomic # = # of Protons = # of Electrons

How do you find the mass #?

Protons + Neutrons

Fill in the table:

Element	Atomic #	# Protons	# Electrons
K	19	19	19
			5
s	16
V		23

Element	Atomic #	# Protons	# Electrons
K	19	19	19
B	5	5	5
s	16	16	16
V	23	23	23

How do you find the number of neutrons?

Mass # - Atomic #

What does each number here mean:

197/79 Au

Top number is: Mass #

Bottom number is: # of protons