Unit 3 - The atom and chemical substances

What charge do protons have?

Is H2 a simple substance or an element?

Every chemical elements is made up by the same atoms.

Democritus knew that atoms were divisible and were formed by subatomic particles.

How is the net charge of the atoms?

Symbols of the chemical elements: Hydrogen is [blank_start]H[blank_end] [blank_start]Carbon[blank_end] is C Copper is [blank_start]Cu[blank_end] [blank_start]Nickel[blank_end] is Ni [blank_start]Calcium[blank_end] is Ca Sodium is [blank_start]Na[blank_end] [blank_start]Aluminium[blank_end] is Al Gold is [blank_start]Au[blank_end] Iron is [blank_start]Fe[blank_end] [blank_start]Sulfur[blank_end] is S Magnesium is [blank_start]Mg[blank_end] [blank_start]Silver[blank_end] is Ag

Anion is an ion with more electrons than protons

- Atomic nucleus: its formed by [blank_start]protons[blank_end] and neutrons, and it's in the [blank_start]middle of the atom[blank_end], occupying a very [blank_start]small[blank_end] space relative to the rest of the atom. - [blank_start]Rest of the atom[blank_end]: also called the shell. [blank_start]Electrons[blank_end] occupy the empty space around each atomic nucleus. Scientists thought electrons [blank_start]orbited[blank_end] the nucleus.

The atomic mass number is the sum of the number of neutrons and electrons

Se+ is...