Chemistry worksheet focusing on the periodic table, featuring questions on element symbols, names, atomic structure, and material properties.

Explanation:
Let’s go through each question one by one and fill in the correct answers using basic chemistry knowledge.

① Define a family.
In the periodic table, a *family* (also called a *group*) is a vertical column of elements that have similar chemical properties because they have the same number of valence electrons.

② What is a period?
A *period* is a horizontal row in the periodic table. Elements in the same period have the same number of electron shells (energy levels).

③ Symbols for elements:
a) Magnesium → Mg
b) Potassium → K (from Latin *kalium*)
c) Iron → Fe (from Latin *ferrum*)
d) Copper → Cu (from Latin *cuprum*)

④ Names for symbols:
a) C → Carbon
b) Cl → Chlorine
c) Au → Gold (from Latin *aurum*)
d) Sr → Strontium

⑤ The number of protons in an atom is that element’s atomic number.

⑥ The number of protons and neutrons in an atom is that atom’s mass number.

⑦ The ability of a material to be drawn into a thin wire is called ductility.

⑧ The ability of a material to be pounded into thin sheets is called malleability.

⑨ Label as metal, nonmetal, or metalloid:
a) Ductile → metal (only metals are ductile)
b) Chlorine → nonmetal (Group 17 halogen)
c) Semiconductor → metalloid (e.g., silicon, germanium—metalloids often act as semiconductors)
d) Malleable → metal (metals are malleable)
e) Cobalt → metal (transition metal)
f) Brittle → nonmetal (nonmetals tend to be brittle when solid; some metalloids too, but generally brittle = nonmetal unless specified like arsenic—but here it's a property, so best answer is nonmetal)
g) Oxygen → nonmetal
h) Good conductor of heat → metal (metals conduct heat well)

Double-checking:
- Ductile, malleable, good conductor of heat → all characteristic of metals.
- Chlorine, oxygen → gases, nonmetals.
- Cobalt → transition metal.
- Semiconductor → metalloid (e.g., Si, Ge).
- Brittle — while some metalloids are brittle, in general classification exercises, “brittle” as a standalone property points to nonmetal (e.g., sulfur, phosphorus). So we’ll use nonmetal.

Final Answer:
① A family is a vertical column (group) of elements with similar chemical properties.
② A period is a horizontal row of elements with the same number of electron shells.
③ a) Mg b) K c) Fe d) Cu
④ a) Carbon b) Chlorine c) Gold d) Strontium
⑤ atomic number
⑥ mass number
⑦ ductility
⑧ malleability
⑨ a) metal b) nonmetal c) metalloid d) metal e) metal f) nonmetal g) nonmetal h) metal