1.The periodic table organizes the elements
according to their physical and chemical
properties.
2. Atomic number = number of protons in each
atom of the element
3. Atomic number
4. (a) 2
(b) 8
(c) 26
(d) 79
(e) 92
(f) 101
5. An atom of potassium
6. Atomic mass is the average mass of the atoms
of an element.
7. Atomic mass units
8. Atomic mass generally increases from left to
right and from top to bottom through the
table.
9. (a) 6.9 amu
(b) 28.1 amu
(c) 55.8 amu
(d) 63.5 amu
(e) 200.6 amu
10. Lead
11. The element is phosphorus. It has 15 electrons
and 16 neutrons.
12. The mass number is 85. It has 37 electrons.
13. Atomic number is the number of protons in
the nucleus, and it is always a whole number.
Atomic mass is the average mass of an atom
of an element. It includes the mass of protons
and neutrons in the nucleus, and it is written
as a decimal number.
14. Hydrogen is unique because it reacts like a
metal in some situations, and like a non-metal
in others.
15. Like other metals, transition metals conduct
heat and electricity, and they are malleable
and ductile.
16. Alkali metals are very reactive, so they are
almost always found in compounds with
other elements.
17. Metals, non-metals, and metalloids
18. (a) Alkali metals, alkaline earth metals,
halogens, and noble gases
(b) Alkali metals and alkaline earth metals
(c) Halogens and noble gases
19. Any five of boron, silicon, germanium, arsenic,
antimony, tellurium, polonium, and astatine
20. Periods
21. Families or groups
22. Alkali metals
23. Alkaline earth metals
24. Halogens
25. Chemically unreactive (usually), gases, colourless
and odourless at room temperature