a. A horizontal row is called a period, with elements listed in order of increasing atomic numbers.
b. A vertical column is a group, with elements that have similar properties.
14. Sodium (Na) and rubidium (Rb).
15.
a. The noble gas family is located on the last row on the right side of the periodic table.
b. Noble gases are unreactive.
c. Noble gases are chemically inert.
16.
a. MgF2
b. GaP
17. In order to estimate the melting point of potassium (K), you need to average the melting points of sodium (Na) and rubidium (Rb).
98+39=137
137/2=68.5
So, the melting point of potassium is aobut 68.5 degrees celsius.
18. I think the boiling point of iodine is higher than the boiling point of chlorine. Usually, if the atomic weight for an element is high, it's boiling point is also higher than elements with low atomic weights. Therefore, since iodine's atomic weight is 127 and chlorine's atomic weight is 35, I think iodine has a higher boiling point.
19.
|
Element Symbol
|
Number of Protons
|
Number of Neutrons
|
Number of Electrons
|
|
C
|
6
|
6
|
6
|
|
C
|
6
|
7
|
6
|
|
Ca
|
20
|
21
|
20
|
|
Pt
|
78
|
117
|
78
|
|
U
|
92
|
146
|
92
|
20.
a. berylium: 4 protons, 4 or 5 neutrons, 4 electrons.
b. nitrogen: 7 protons, 7 or 8 neutrons, 7 electrons.
c. neon: 10 protons, 10 or 11 neutrons, 10 electrons.
21. This student is confused because an atom can only gain or loose electrons, the protons always stay the same. Therefore, in order to create a lead atom with 2+, the atom lost two electrons, to become positive.
22.
a.
carbon: 12
calcium: 41
platinum: 195
uranium: 238
b. Carbon has two isotopes in the periodic table.
23. The mass number is not sufficient enough to justify the claim of the discovery of a new element. It would be more helpful to know the atomic weight of eh atomic number of the element rather than the mass number.
24. The mass of an electron is much less than a proton or a neutron; it is about 1/2000 the mass of a proton or a neutron.
25.
|
Isotope Symbol
|
Mass Number
|
Number of Protons
|
Number of Neutrons
|
|
Mg-24
|
24
|
12
|
12
|
|
Mg-25
|
25
|
12
|
13
|
|
Mg-26
|
26
|
12
|
14
|
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