Why do filaments of bulbs heat up?

[Jimmy87]

Homework Statement

This is not entirely a homework question but more a question about a homework assignment. We were asked to find out why a filament of a bulb heats up by talking about microscopic ideas. This is a link to a website that contains the relevant information under the heading 'higher tier only'

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/resistancerev4.shtml

Homework Equations

None

The Attempt at a Solution

I just wanted to ask if the electrons collide with metal IONS or metal ATOMS. I have found other sources that have said the electrons collide with the metal atoms and surely only one is correct. I thought a metal ion is when an atom has completely had an electron removed. I thought conductors just have electrons that are free to drift rather than electrons that have been completely removed?

 

[ehild]

The metal atoms are ionized in the metal. Their outermost electrons leave their parent atoms and belong to the whole metal, moving about freely.
Ion is a charged particle, it contains more or less electrons than there are protons in the nucleus. The metal is usually neutral, the electrons are not completely removed from it, they are removed only from the atoms.