Atoms, elements and compounds Flashcards
(36 cards)
What is an atom?
An atom is the smallest part of an element that can exist
Represented by a chemical symbol starting with a capital letter (1 or 2 letters)
About 0.1nm
What is an element?
A substance made up of only one type of atom.
What is a compound?
A substance which contains 2 or more elements chemically combined in fixed proportions.
Compounds have different properties than the elements that make them.
They can only be separated into elements using chemical reactions
Example
Iron + Oxygen —> Iron oxide
Facts about chemical reactions.
Chemical reaction always involve the formation of one or more new substances and often involve an energy change.
How do you balance a chemical equation?
Count the amount of each atom on either side.
Add atoms on either side until the equation becomes equal.
Formula for:
Carbon dioxide
Water
Oxygen
Hydrogen
Nitrogen
Ammonia
Hydrochloric acid
Sulfuric acid
CO2
H20
O2
H2
N2
NH3
HCL
H2SO4
What are the 3 types of particles that make up an atom?
Protons - positive charge
Neutrons - No charge
Electrons - Negative charge
What is the relative charge and mass for protons, neutrons, and electrons?
Protons - charge + 1, mass 1
Neutrons - charge = 0 mass 1
Electrons - charge -1 mass 1/2000
Key facts about number of protons in an element
Atoms of different elements have different numbers of protons
All atoms of a particular element have the same number of protons
What is an isotope?
Atoms of the same element that have the same number of protons but a different number of neutrons
What is an ion?
An ion is a charged particle which is formed when an atom gains or loses electrons
How to name Ionic compounds (Metal + Non metal) and (Metal + Non - metal + Oxygen)
Metal + (First syllable of nonmetal) - ide
Metal + (First syllable of nonmetal) - ate
What is a mixture?
2 or more elements or compounds not chemically combined together.
Can be separated using physical processes
5 different physical processes
Filtration
Crystallisation
Simple distillation
Fractional distillation
Chromatography
Describe filtration
Used to separate insoluble solids from a liquid
A funnel with filter paper is placed in a conical flask
Mixture gets filtered through filter paper (filtrate).
Describe crystallisation
Used for separating soluble solids and liquids
Place solution in evaporating basin
Gently heat so most of the water evaporates
Leave rest to evaporate and cool
Salt crystals are left behind
Describe distillation
Used to separate 2 liquids according to boiling point
Heat mixture until 1st liquid evaporates (reaches boiling point)
Collect condensed liquid in beaker
Describe fractional distillation
Used to separate multiple liquids according to boiling points
Increase temp to the lowest boiling point, and increase to next when liquid is distilled
Component liquids will distill one by one in order of boiling point.
Vapors condense in condenser before being collected in beaker
Describe chromatography
Clip paper to toothpick using paperclip
Draw pencil line near bottom of paper
Draw a range of dots using different inks along the line and label with pencil
add small amount of water to beaker so the water level is almost touching the line
Radius of atom and nucleus
Radius - 1x10^ -10m (0.1nm)
Nucleus - 1 / 10000 radius
What is Dalton’s model?
Atoms are solid spheres that cannot be broken down any further.
What is JJ Thompson’s plum pudding model?
Electrons are smaller negative charges inside a large ball of positive charge
What is Rutherford’s alpha scattering experiment
Fired positive alpha particles at a 1 atom thick sheet of gold foil
Most went straight through, some were deflected (mass is concentrated in the nucleus and is positively charged)
This shows MOST of the atom is empty space/
What do electrons do?
They orbit the nucleus at fixed distances
