#1: how are the elements arranged in the modern periodic table?

a. by increasing atomic mass
b. by decreasing atomic mass
c. by increasing atomic number
d. by decreasing atomic number

#2: which of these sets of elements has similar properties?

a. hydrogen, helium, neon
b. oxygen, nitrogen, carbon
c. strontium, magnesium, calcium, beryllium
d. chromium, magnesium, iron, cobalt

#3: which element has properties most similar to sodium?
a. potassium
b. calcium
c. aluminum
d. neon

#4: why didn't mendeleev include helium, neon, and argon in his periodic table?
a. these elements did not fit in with his pattern.
b. these elements are gases and he didn't include gases.
c. the atoms of these elements had no atomic mass.
d. these elements had not yet been discovered.

#5: the periodic law describes trends seen across which of the following?
a. the top half of periodic table
b. periods within the periodic table
c. radioactivity within the periodic table
d. elements with the same number of protons