C1-3 Flashcards
Particle model doesn’t show:
- forces between particles
- size of particles
- space between particles
Electrostatic forces of attraction
Between positive & negative charges of particles
Weaker further apart (gases)
Chemical & physical changes examples
Chemical:
- cooking
- steel rusting
- acid reacting with alkali to make salt & water
Physical:
- freezing
- mixing sand with water
- dissolving sugar/salt in water
Atom
Smallest particle of an element that still has its chemical properties
Molecules
Made from 2+ atoms joined together by chemical bonds
Bond length
Distance between centres of 2 joined atoms (radius + radius)
Atomic number
No. Of protons in nucleus (& how many electrons)
Mass number
Total no. Of protons & neutrons
= atomic number + no. Of neutrons
Isotopes
Atoms with same no. Of protons & electrons, but diff no. Of neutrons
(Same atomic number, diff mass number)
Why do groups in periodic table have similar chemical properties
Same no. of electrons in outer shell
Ions
Charged particles formed when atoms / groups of atoms lose/gain electrons
Relative atomic mass (Ar)
Mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom
(>12 = more mass than carbon-12 atom) (<12 = less mass than carbon-12 atom)
Relative formula mass (Mr)
Mean mass of unit of substance compared to 1/12 mass of carbon-12 atom
= add together Ar values
empirical formula
Shows simplest whole number ratio of atoms of each element in a compound
Pure substance
Consists of just 1 element or compound
Melting points:
- higher
- single temperature
