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'
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?