6.2 metals

• Science
• Middelbare school
• vwo
• Leerjaar 3

par 6.2 metals

you will learn

• characteristics of metals at  macro level
• explain properties of metals at micro level
• what alloys are and why they have different properties

molecular substances consists of metals and non-metals.

1. yes
2. no

Salts are built from metals

1. yes
2. no

Metals conduct electricity when ......

1. solid
2. liquid
3. solid and liquid
4. never

Molecular substances conduct electricity in solid phase.

1. yes
2. no

salts conduct electricity in liquid phase.

1. yes
2. no

95 metals in the periodic table

Alle metalen zijn rood omlijnd

properties of metals

Metals are always ...

• ... shiny in pure form;
• ... good conductors for electricity and heat
• ... malleable, especially when they are hot;
• ... can, when molten, be mixed with other metals. (alloy)

shiny bolts

conductive cupper wire

malleable iron

bronze church clock

properties of metals 

Metals ...

• ... are not all hard; potassium
• ... not alle have a high density; sodium
• ... not all have a high melting point ; gallium
• ... are dangerous for health or environment: lead

you can cut potassium

sodium floats on water

lead is poisonous

gallium melts in your hand

Corrosion of metals

• Corrosion: metals reacting wirh water and oxygen.
• Corrosion of iron : rusting
• Not all metals react in the same manner with water and/or oxygen.

sodium

iron

highly reactive metals

reactive metals 

semi-precious metals

silver

precious metals 

gold

Metals at micro level

to conduct electricity you need:

- substances with charged particles

- these particles must be able to move freely

- both conditions have present at the same time. 

Metals at microlevel 

• An atom contains a nucleus surrounded by electrons
• nucleus contains protons and neutrons
• Protons are positively charged, elctrons are negativiely charged
• An atom contians same amount of protons and electrons
• Amount of protons defines type of atom
• electrons in the outer shell are called valence electrons

Metallic lattice

sodium lattice

meerdere natriumatomen vormen een metaalrooster

Metallic lattice 

• valence electrons can move freely through the lattice, they no longer belong to one atom

Schematische voorstelling van een metaalrooster met (positieve) ionen en (negatieve) elektronen

solid versus liquid

• In a metal lattice of a solid the particles are closely packed, valence electrons can move easily through the metal.
• In liquid phase there is no longer a lattice but the particles are still close together. Valence electrons can still move easily                                                                                  through the metal. 
• This explains why solid and liquid                                                                                 metals are good electric conductors.

alloys 

• Molten metals can be mixed → alloy

Messing

Bronze

Duraluminium

stainless steel

malleability of metals

pure metals are better ductable than alloys

In a pure metal the lattice is malleable because all the particles have the same size.

In an alloy the particles have different sizes. So an alloy is less malleable.

Which metal is a precious metal?

1. Au
2. Na
3. Fe
4. Cu

Why can calcium conduct electricity?
( on a micro level)

1. Metals always conduct electricity
2. In a metal lattice there are free electrons
3. Metals have a positve nucleus
4. electric current is a movement of electrons

Can an alloy conduct electricity?

1. No because the mdetal lattice is disturbed
2. yes, because an alloys stills meets the conditions for conductivity
3. no because electrons of two metals are mixed
4. yes but only when there are no non-metals present in the alloy.

read par 6.2

do q  par 6.2