What are the physical and chemical properties common to all Group 1 (alkali) metals?
Physical: They are soft, have low densities and have relatively low melting/boiling points.
Chemical: They are highly reactive and must be stored in oil to prevent reaction with oxygen or moisture in the air
Describe the trends in reactivity and melting points as you go down Group 1
Reactivity: Increases down the group (Lithium is the least reactive; Francium is the most).
Melting/Boiling Points: Decrease down the group.
Why do all alkali metals have similar chemical properties and form 1+ ions?
They all have one electron in their outermost shell. They react by losing this single electron to achieve a stable noble gas structure, resulting in a 1+ charge. Reactivity increases down the group because the outer electron is further from the nucleus and more easily lost.
What are the products when an alkali metal reacts with water?
Metal hydroxide (alkali) + Hydrogen gas. The metal floats, fizzes (effervescence), and moves on the surface.
What are the physical properties common to the halogens?
- They are non-metals with colored vapors.
- They consist of diatomic molecules (pairs of atoms joined by a covalent bond)
- They are poor conductors of heat and electricity.
- They have low melting and boiling points.
Describe the trends in melting points and reactivity as you go down Group 7.
Melting/Boiling Points: Increase going down the group (molecules get larger, so intermolecular forces get stronger).
Reactivity: Decreases going down the group (it becomes harder to gain an electron as the outer shell is further from the nucleus).
How many electrons do halogens have in their outer shell, and what ions do they form with metals?
They have seven electrons in their outermost shell.
To achieve a stable noble gas structure, they gain one electron to form ions
They form ionic compounds with metals and covalent bonds with non-metals (by sharing electrons).
State the rule for halogen displacement reactions.
A more reactive halogen will displace a less reactive halogen from solutions of its salt
What happens to the size of atoms as you move down any group in the Periodic Table?
Atoms become larger. This is because the number of occupied electron shells increases by one for each extra period you go down.
What is the “shielding” effect in an atom?
Atoms get larger, so the outer shell is further from the nucleus. Increased distance and shielding make it harder for the nucleus to attract and gain an incoming electron.
