How many significant figures are in the measurement 0.00440 grams?
6
5
3
2
What is a possible formula of a compound formed when sodium and chlorine bond?
NaCl4
NaCl3
Na2Cl3
NaCl
A neutral atom has an atomic number of 14 and a mass number of 30, how many protons, neutrons, and electrons are found within the atom?
30 protons, 14 electrons, and 30 neutrons
14 protons, 14 electrons, and 16 neutrons
14 protons, 16 electrons, and 16 neutrons
30 protons, 30 electrons, and 14 neutrons
3 Answers
0.00440 g … the first two zeroes are not significant, they are just place holders. The remaining three digits are all significant.
Na forms a +1 ion and Cl forms a -1 ion. So you need 1 Na+ for every 1 Cl- … NaCl.
Atomic number = no. of protons = number of electrons (in a neutral atom) = 14. Mass number =
no. of protons + no. of neutrons. No. of neutrons = mass no. – no. of protons = 30 – 14 = 16.
3
NaCl (Na+ + Cl-)
14 protons, 14 electrons, 16 neutrons (atomic number = # protons and electrons, mass number-atomic number = # neutrons)
3 significant figures
NaCl
14,14,16