Atom Flashcards
Define element
A substance that is made from 1 type of atom / A substance that cannot be chemically broken down to simpler substances.
Example: O
Define compound
A substance that is made up of 2 or more atoms chemically bonded to each other.
Example: MgO
Define mixture
2 or more substances dissolved into each other, and each of them still has its own properties.
Define solution
2 or more substances dissolved perfectly into each other as if they combined together already. They are a homogeneous mixture.
Atoms are made from
Electrons, protons and neutrons.
The first electron shell of an atom can hold a maximum of how many electrons?
2 electrons
The second, third, and so on electron shells of an atom can hold a maximum of how many electrons?
8 electrons
Atomic number is
Number of proton(s) in that atom.
Atomic mass is
Number of proton(s) + neutron(s) in that atom.
Define isotope
Another version of an atom, they are all the same element but each of them has a different number of neutrons.
Can isotopes of an atom have different chemical properties?
No. They have:
- The same number of protons and electrons => No differences in charges
- The same number of electrons in the outer shell => Will react to other elements in the same way.
Can isotopes of an atom have different physical properties?
Yes.
- Different number of neutrons => Different masses
- Some nuclei are unstable and can be radioactive.
Define relative atomic mass
Symbol of relative atomic mass
Because there are isotopes of elements so we just take the average mass of them as the mass of the element. This is the relative atomic mass.
Symbol: Ar (subscript r)
Heavier atoms/molecules will diffuse slower than lighter atoms/molecules. True/False?
True
