Chapter 19: Elements and Their Properties
Section 1: Metals
1. Metals are good conductors of electricity, and of heat. Electricity is the conduction of valence electrons from one atom to another
Metals conduct heat:
The atoms in a substance are always vibrating. When heat is applied to a substance the heat energy is given to the atoms and they vibrate and move faster and so their kinetic energy increases. The vibrating atoms bump into neighboring atoms and pass on their kinetic energy. These atoms then pass on their kinetic energy to atoms close to them and so on. In this way the heat energy moves through the substance.
Conduction takes place in solids, liquids and gases, but works best in solids as their atoms/molecules are located closer together.
Metals are the best solids for conducting heat.
Metals have tightly packed atoms which can easily pass on their kinetic energy and also have free moving electrons.
These electrons can move from the hot part of the metal to the colder part transferring the energy more quickly.
Poor conductors or insulators do not possess free moving electrons.
2. Fresh cut metal has a high luster/sheen.
Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning “light”. A range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky.
3. Most metals are solid at room temperature.
4. Ductile – metals can be drawn into wires. In this image, reddish copper is inside a steel cup, with a small hole. Pressure is being applied to the copper – and a small amount is pushed out through the hole. A tool grabs this exposed copper, and slowly pulls. As it pulls, more and more copper is drawn out in a tube.
5. Malleable – can be hammered into thin sheets without breaking
Malleability is a material’s ability to deform under compressive stress; this is characterized by the material’s ability to form a thin sheet by hammering or rolling
6. Metals deform because atoms can slide past each other, while still maintaining bonds. How is this possible?
A metallic bond is a lattice of positive ions, immersed in a sea of electrons. The ions here are entire atoms: the nucleus, and many of it’s electrons, still tightly bound to their parent atom.
The ‘sea’ around them are the valence electrons: valence electrons are the outermost electrons. They are not tightly bound to their home atom.
Valence electrons freely flow through solid metal, as if they are a gas!
If an object (like a hammer) slowly pushes into the metal, we see the atoms move. Yet the atoms are still bonded to each other through this sea of valence electrons.
Section 2: Non-metals
1. Non-metals are not good conductors of electricity or heat
2. Do NOT have a high luster/sheen
3. Most are gases at room temp
4. NOT ductile – can NOT be drawn into wires
5. NOT malleable – can NOT be hammered into thin sheets without breaking
This means that they are BRITTLE
Mixed properties: Metalloids
1. Have properties in-between those of metals and non-metals
2. Under specific conditions, a metalloid may behave like a metal or non-metal
3. We can easily control how a metalloid behaves by changing the conditions:
Just evenly mix a small amount of another element into the metalloid
By controlling how much of this new element we add, we can control the exact properties of the metalloid. This makes them useful in creating semiconductors.
Hydrogen is in its own special category
Not a metal. yet not a non-metal
1. colorless, odorless, nonmetallic, tasteless
2. highly combustible
3. Diatomic gas -> molecular formula H2
4. the lightest element
5. Most abundant chemical element: makes up 75 % of the Universe’s mass