Unit 1 Part 1 Flashcards
What is the difference between a physical and chemical change?
Physical changes are usually reversible (eg: changes of state).
Chemical changes are usually permanent and always produce a new substance.
Define Exothermic
Define Endothermic
Exothermic : Releases heat
Endothermic : Takes in heat
Define a catalyst
Catalysts are used to speed up a reaction rate which can be recovered unchanged.
Equation to measure rate of reaction
change in property
——————————
change in time
Describe the structure of an atom
Nucleus contains protons and neutrons. Electrons orbit around in different energy levels.
What are ions?
A changed particle
How are ions formed?
When an atom gains or loses electrons
Why do atoms for ions?
to achieve a stable electron arrangement
What can be said of the balance of protons and electrons in an atom compared to an ion?
atoms have equal amounts of protons to electrons
ions don’t have an equal amount for protons and electrons
Why are atoms neutral?
the protons and electrons cancel out
What’s the electron arrangement of any atom?
2
8
8
18
In Nuclide notation where does the mass number go?
Top left
How do you find the mass number?
Number of protons + number of electrons
In nuclide notation where do you find the atomic number?
Bottom left
How do you find the atomic number?
Number of protons
What are isotopes?
Atoms of the same element which have different mass numbers
Isotopes have different numbers of neutrons
On the periodic table, where do you find the atomic number
Above the letter
What’s the valency equal to?
valency = charge
What is RAM
Relative atomic mass
Define RAM
the average mass of the isotopes present taking into account their relative proportions.
What’s the most common isotope
Carbon
Which atom is the atom against which all mass of all other atoms are compared to?
Carbon
6P , 6N, 6E
How do you calculate RAM?
total mass of all atoms present
————————————————
number of atoms present
(% abundance X mass of isotope) + (same )
————————
100
What is covalent bonding?
a chemical bond that involves the sharing of electron pairs between atoms
What’s it called when’s. covalent bond shares 2 pairs of electrons?
Double covalent bond
What are the different structures?
Linear
Angular
Pyramidal
Tetrahedral
What are discrete covalent molecules?
small and contain the number of atoms indicated in the formula, eg: CO2 has 3 atoms
What is a covalent network?
giant structure with a huge number of atoms
What is an intermolecular force?
weak forces of attraction
Define ionic bond
when one element donates an electron (or electrons) to another so that both elements will have a full outer shell.
a metal transfers an electron to a non metal
Define metallic bonding
Metallic bond, force that holds atoms together in a metallic substance.
How are atoms of a metallic bond arranged?
Metals consist of giant structures of atoms arranged in a regular pattern. The electrons from the outer shells of the metal atoms are delocalised , and are free to move through the whole structure.
What’s special about electrons in metals?
They can move freely
Covalent networks have a
_____ melting point
high
What’s broken in covalent networks?
strong covalent bonds
Do covalent bonds conduct electricity?
No, except graphite
Covalent molecules have a ____ melting point?
low
What’s broken in covalent molecules?
weak intermolecular forces
Are covalent networks soluble in water?
no insoluble
Do covalent molecules conduct electricity?
doesn’t conduct electricity in any state
Are covalent molecules soluble in water?
they’re more likely to be soluble
Ionic lattices have a ____ melting point
high
What’s broken in an ionic lattice?
strong ionic bonds
Do ionic lattices conduct electricity
only melted or in solution
Are ionic lattices soluble in water?
more likely to be soluble
