p. 130, #13-25

13.
a. row: (horizontal) periods that are grouped according to the increase in atomic number
b. column: (vertical) groups that are organized by elements with similar properties

14.
. Hydrogen (H)
. Sodium (Na)

15.
a: Noble gasses are located on the far left side of the periodic table - the last group
b: Noble gasses are all in a gas state at room temperature
c: Noble gases are all nonreactive with other elements

16.
a. Mg and F: MgF2
b. Ga and P: GaP

17. My estimated melting point of K is about 68.5 degrees celsius. I found this by averaging 98 degrees celsius and 39 degrees celsius.

18. I would expect the boiling point of iodine to be higher than that of chlorine because iodine has a higher atomic number than chlorine.

19. See on paper

20. See on paper

21. If the lead atom gained two protons to make the ion, it would have changed into another element. If the number of protons changes, the element transforms into another element. The only way an ion can be formed is through the loss or gaining of electrons. The way that the lead ion was formed was by losing two electrons.

22.
a:
- Be: 9
- N: 14
- Ne: 20
b: Carbon has two isotopes

23. No, the mass number does not prove that there is a new element. In order for the element to be added to the periodic table, we must be aware of its physical and chemical properties along with the number of protons, neutrons, and electrons.

24. The mass of an electron is much less than the mass of a proton and a neutron. It does not contribute that much to the atomic mass.

25.
. Mg-24: protons: 12 neutrons: 12
. Mg-25: protons: 12 neutrons: 13
. Mg-26: protons: 12 neutrons: 14