Periodic Table Flashcards
(20 cards)
Metallic character on a period decreases_____________and increases_________
From left to right across a period
From right to left across a period
Metallic character in a group increases____________and decreases_______
As up go down the group
As you go up the group
All metallic elements
Have outer shells electrons 1-4
Group 1 metals…
-Are soft
-Melting and boiling points decrease as you go down the group (they become more reactive as you go down the group)
They have LOW MELTING AND BOILING POINTS
-rate of reaction increases as you go down the group
-The density increases as you do down the group
-Gets softer as you go down the group
-Because of their extreme reactiveness they are stored in oil
(To prevent reaction with air )
The periodic table is…
….a method of classifying elements that is used to predict properties of elements
Lithium, sodium and potassium…
Are all group 1 metals, alkali metals. This is because when they react with water they produce alkaline solutions, metal hydroxide is formed when alkaline metals react with water.
Chlorine, bromine and iodine…
Are all halogens in group 7
Trends in Group 7 elements: Melting and boiling points
Melting point and boiling point
The halogens have low melting points and boiling points. This is a typical property of non-metals. The melting points and boiling points then increase as you go down the Group.
Trends in Group 7 elements: colour
Colour
The halogens become darker as you go down the group. Fluorine is very pale yellow, chlorine is yellow-green and bromine is red-brown. Iodine crystals are shiny purple-black but easily turn into a dark purple vapour when they are warmed up.
Trends in Group 7 elements: reactivity
Decrease as you go down the group fluorine is the most reactive.
F &Cl are gases
Br is a liquid
I & At are solids
Why does the reactivity increase as you go down the group?
All alkali metals have one electron in the outer shell. In a reaction, this electron is lost and the alkali metal forms a +1 ion. As you go down group 1, the number of electron shells increases – lithium has two, sodium has three etc. Therefore, the outermost electron gets further from the nucleus. The attraction from the positive nucleus to the negative electron is less. This makes it easier to remove the electron and makes the atom more reactive.
Reactions with metals
The halogens react with metals to make salts called metal halides.
metal + halogen → metal halide
For example, sodium reacts with chlorine to make sodium chloride (common salt).
sodium + chlorine → sodium chloride
2Na(s) + Cl2(g) → 2NaCl(s)
The reaction between sodium and a halogen becomes less vigorous as you move down Group 7. Fluorine reacts violently with sodium at room temperature. Chlorine reacts vigorously when in contact with hot sodium. Iodine reacts slowly with hot sodium.
Halogens: conduct electricity?
Halogens are all poor conductors of heat and electricity – typical of non–metals.
Trends of group 7 elements: density
The density of the halogens increases down Group 7 halogens.
Note on naming halogen compounds:
When halogens combine with other elements in simple ionic compounds the name of the halogen element changes slightly from …ine to …ide.
Fluorine to fluoride etc.
Reactions with other halides:
When you add Chlorine water to a solution of Potassium Bromide, the solution turns orange. This reaction is taking place:
Cl2 (aq) + 2KBr (aq) —-> 2KCl (aq) + Br2 (aq)
Chlorine + Potassium Bromide —> Potassium Chloride + Bromine
This is called displacement.
Bromine has been, what we called, Displaced for a more reactive halogen. It’s a bit like how girlfriends and boyfriends function nowadays. Girl A is with Boy A. The more attractive male, Boy B comes along and displaces Boy A.
Displacement is when:
What this means is that when a halogen reacts with a salt such as Potassium Bromide (one that contains a -ide), the more reactive halogen will take the place of the less reactive halogen, as we clearly saw in the example just now. Chlorine is definitely more reactive than Bromine, as it is higher up in the Group and reactivity decreases down a group, so it displaces the Bromide in the salt to form Potassium Chloride.
Transition metals:
- Have high densities
- High melting points
- Form coloured compounds
- Often act as catalysts in elements and compounds
Noble gases (VIII)
- unreactive because they have full outer shells, so they are stable
- monoatomic gases, exists as one atom
Uses of noble gases:
-argon is used in lamps
Used in light bulbs. The very thin metal filament inside the bulb would react with oxygen and burn away if the bulb were filled with air instead of argon. Argon stops the filament burning away because it is unreactive.
-helium is used to fill balloons and is used in airships.
Used in balloons and airships. It is much less dense than air, so balloons filled with it float upwards.
-Neon
Used in advertising signs, it glows when electricity is passed through it. Different coloured neon lights can be made by coating the inside of the glass tubing of the lights with other chemicals.
-Krypton
Used in lasers. Krypton lasers are used by surgeons to treat certain eye problems and to remove birthmarks.
