Topic 3 Atoms, Element, Compounds Flashcards
Signs of chemical change (4)
temperature change
gas produced
changes in colour
percipitation/solid formed
Define physical reactions
reaction that involves change of state but no new substance is made
Physical substances are often easy to go back to the original substance.
True or false
true
What are reversible reactions indicated by?
⇌
Word equation for hydrated copper(II) sulfate
hydrated copper(II) sulfate ⇌ anyhdrous copper(II) sulfate + water
Word equation for hydrated cobalt (II) chloride
hydrated cobalt (II) chloride ⇌ anhydrous cobalt(II) chloride + water
Describe the colour change in hydrated copper(II) sulfate when it is heated and then water added again.
Hydrated copper(II) sulfate is BLUE
When heated, anhydrous copper(II) chloride formed. Colour is WHITE
If water is added, hydrated copper(II) sulfate formed again. Colour is blue.
Describe the colour change in hydrated cobalt(II) chloride when it is heated and then water added again.
hydrated cobalt(II) chloride is PINK
when heated, it forms anhydroous cobalt(II) chloride formed. Colour is BLUE
Adding water reconstructs hydrated cobalt(II) chloride. Colour is PINK
Define an element
substance containing only one type of atom
Define compound
substance containing two or more types of atoms chemically joined toether
Define mixture
Contains more than one substance but the substances are not chemically joined together
Features of metals (6)
conducts heat and electricity
malleable (easily bent or shaped)
shiny
sonorous (rings when struck)
ductile (stretches into a wire)
high melting and boiling point
Features of non-metals (4)
poor conductor of electricity
brittle
dull
low melting and boiling points
What are alloys
Formed when emtals are mixed with other elements
Define a solution
type of miture that is formed when one substance dissolves fully in another
define solute
substance that is dissolved
define solvent
substance which does the dissolving
Define concetration + units (2)
measure of how much solute is dissolved in the solvent
mol dm^-3 or moles per dm^3
Name the 3 sub-atomic particles
Proton
neutron
electron
Describe proton (3)
positive charge
Found within the nucleus of the atom
mass of 1
Describe neutron (3)
no charge
found within the nucleus of the atom
mass of 1
Describe electrons (3)
negative charge
found in the electron shells which orbit the nucleus
mass of about 1/2000
What is the overall charge of an atom
no over charge (number of protons = number of electrons)
The number of protons = number of electrons
True or false
True
Proton numbers are also known as ________
Atomic numbers
Nucleon numbers are also known as _____
mass numbers
How to find nucleon number
nucelon = proton + neutrons
How are electrons arragned in an atom
arranged in shells around a nucleus
The arrangement of electron is also knwon as ________ __________
electronic configuration
Describe noble gases (2)
full outer electron shell
stable ( doesn’t react)
Define valence electrons
outer electrons of an element that are involved in chemical bonding
Why do element in the same group have similar chemical properties
same number of valence electrons
Define periodicity
A trend in a periodic table
Define isotope
Atoms of the same element with the same atomic number but different mass numbers
Why would isotopes of the same element have the same chemical properties?
same number of electrons in their electron shells
What is a chemical behaviour of an element determined by
outer electron shell
Define ion
when an atom loses or gains electrons in order to gain a full outer electron shell, gaining a charge
Define cations
positive charged ions
Define anions
negatively charged ions
How does ionic bonding happen?
forms due to METAL atoms giving their electrons to NON-METAL atoms in order for both atoms to become stable charged particles
Define ionic bond
electrostatic force of attraction between oppositely charged ions
Define ionic lattice
Ions in an ionic compound which are arranged in a pattern
Define oxidation
loss of electrons
Reduction
gain of electrons
Define electricity
flow of charged particles (ions or electrons)
Explain electrical conduction
In metals (+ graphite) it is the outer electrons of the atoms (delocalised electrons) which are able to move and so can carry an electrric current
Why can’t conduction happen in ionic substances if solid
ions held in ionic lattice when solid, ions are not free to move about
How can conduction happen if an ionic substance is dissolved in a solution (or molten)
ionic lattice broken down, allowing the ions to more freely
Define electrolyte
Molten substance or a solution that conducts electricity
Non-metals (except graphite) and covalent substanes are electrical insulators
True or False
True
Properties of ionic substances (5)
hard crystals- Due to strong attraction between positive and negatiev ions ionic substances are crystlline
high melting point- a lot of energy is needed to break the strong forces of attraction between ions
dissolves in water- water can form strong electrostatic attractions with the ions so are plucked off the lattice structure
does not conduct when solid- ions are held tightly in the lattice structure and are not able to move
conducts when molten/in solution- lattice breaks and ionsa re free to move
Define covalent bond
pair of electrons shared by two atoms, the shared part of the electrons holds the atoms together
define molecule
group of atoms held together by covalent bonds
Define valency
number of bonds an element needs to form in order gain a full outer electron shell
What is the valency for each group
1 2 3 4 3 2 1 0
What holds a covalent bond together
protons (positive charged) held within nucleus
electrons (negative charged) held in electron shells outside nucleus
electron and proton attract as opposite charges attract, holding atom together in covalent bond
Define macromolecules
giant structures whose atoms are held together by multiple covalent bond
Define giant covalent structures
giant strucutres whose atoms are held together by multiple covalent bonds
Carbon has two forms which are classed as giant covalent structures. Name the two (2)
diamond
graphite
Explain shape of diamond (2)
carbon atoms arranged in a tetrahedral structure
every carbon is bonded to 4 other carbon atoms by very strong covalent bonds
explain shape of graphite (3)
carbon atoms held in hexagonal shape, in layers
each carbon atoms bonds to three other cabons by strong covalent bonds
weak layers are held together by weak intermolecular forces of attractions
Properties of diamonds (3)
all covalent bonding is strong
high melting point as a lot of energy needed to break this strong bonds
cannot conduct electricity
Properties of graphite (3)
strong covalent bonds between atoms but weak intermolecular forces of attraction between layers
layer can slide over one another, LUBRICANT (substance that minimizes friction)
Conducts electricity because graphtie contains delocalised electron
Properties and explain silicon(IV) oxide (2)
forms 4 strong covalent bonds
high melting point
Define covalent molecular substances
groups of atoms held together in molecules
Properties of covalent molecular substances (4)
low melting and boiling points
volatile (vapourise easily) due to low melting and boiling points
Does not conduct electricity
insoluble in water
Explain why covalent molecular substances have low melting and boiling points (3)
when melted or boiled, the strong bonds between atoms (intramolecular forces) are not broken
Instead the intermolecular forces (weak forces of attraction been molecules) are broken
Intermolecular forces of attraction much weaker than intramolecular forces of attraction
Explain why giant covalent structures have high melting points
every strong covalent bonds must be broken, requring a lot of energy
