chemistry Flashcards
chemistry exam
Which particle determines what element an atom is?
- PROTONS
Which sub-atomic particle does NOT have a charge?
-NEUTRONS
If an atom has 6 protons and 5 electrons, what charge will it have overall?
+1
Which particles within an atom have a relative mass of 1?
PROTONS AND NEUTRONS
Electrons orbit the nucleus in energy …
Electrons orbit the nucleus in energy shells.
What do we call an atom that has a positive or negative charge?
AN ION
An atom has 13 protons and 14 neutrons. What is its mass number?
27
What are isotopes?
Atoms of the same element with different numbers of neutrons
Four atoms have the numbers of protons and neutrons given below. Which two atoms are isotopes of the same element?
Atom W: 11 protons and 10 neutrons
Atom X: 10 protons and 10 neutrons
Atom Y: 9 protons and 9 neutrons
Atom Z: 10 protons and 9 neutrons
X AND Z
Lithium naturally exists as two isotopes: lithium-6, with an abundance of 7.6%, and lithium-7, with an abundance of 92.4%.
6.92
When Democritus first conceived of atomic theory, around 500 BC, how did he describe atoms?
- The smallest possible unit of matter
- Separated from each other by empty space
- Small spheres
In 1897 J. J. Thomson theorised that an atom consisted of a ball of positive charge, with negative electrons mixed throughout it. What do we call this model?
plum pudding model
In the 1800’s, John Dalton described atoms as …..
, and suggested that different types of spheres make up the….
.
- solid sphers
- different elelemnts
In Rutherford’s experiments, alpha particles were fired at a thin sheet of gold foil.
Most particles passed through, but some were deflected off course.
This caused him to hypothesise that there was a dense region of positive charge at the centre of the atom that repelled the alpha particles.
As a result he developed the nuclear model of the atom, in which there was a central positive nucleus, surround by negative electrons.
An atom of oxygen has 6 electrons in the outer shell. In a reaction, it gains 2 electrons.
What is the charge of the oxide ion created?
2-
definition of isotopes?
isotopes are the same element that have the same number of protons but a different number of neutrons.
smallest element in the periodic table?
hydrogen
what do different isotopes have?
- different masses
how do isotopes react even though they have different number of neutrons?
- they react the same way
how to calculate the relative mass of two isotopes?
sum of abundance of all isotopes
what does it mean when an atom is not stable?
doesnt have a full other shell
what do not stable atoms do?
react with other atoms to become more stable
,eaning of stable in electrons
outermost shell is full
define a group in period table with full outer shell
noble gases have a full outer shell
in an exam what do they mean by electron structure?
they mean draw the electron, if it gained an electron put brackets an mines the amount of electrons you gained if you loose the electrons do the same thing with brackets but put a plus whatever the number of electrons you added
what is the first group in the periodic table?
alkali metals
what is group 7 in the periodic table?
halogens
what is the tomic number?
number of protons and neutrons
in the periodic tbale what does a row present?
a period
in the periodic tbake what does a column present?
a group
what do metals form?
when metals react what do they form?
positive ions
when non metals react what do they form?
negative ions or dont form ions
as you go down in the periodic table the metals tend to be more reactive, why is that?
because the elements far down the table have lots of shells, so outermost shell is far from the nucleus it would be harder for the nucleus to keep the electrons and it woudl be easier for the elctrons to loose and make the atom positive
more reactive as they are more likely to loose electrons during a reaction.
what hold the negative electrons in place that doesnt make the collapse?
the positive nuclus in the middle
physical properties of metals: (6)
- mallable- can bent without snapping
- metallic bonding- occurs only in metals and very strong
- good conductors of heat and electricity- thats why we use them in electric wires
- high melting and boiling point
- shiny
- sonorous
physical properties of non metals: (5)
- dull in colour
- brittle easily break
-low melting and boiling point - lower density so weight less for different volume
- poor conductors of electricity
where are transition metals found?
centre if periodic table in the middle of group 2-3
transition metals
normal metals with extra properties:
- can form more than once ion that have their own section
- coloured: transition metal ions are colored
- good catalysts
what is a catalyst?
substance that speeds up a chemical reaction without being used up
Alkali metals react with water. Which two products are formed?
Alkali metal + water ➔ metal hydroxide + hydrogen
Explain why the reactivity of group 1 metals increases as you go down the group.
The reactivity of group 1 elements increases as you go down the group because the atoms become larger, which means that the outer electron becomes further from the nucleus.
This in turn means that the electrostatic attraction between the positive nucleus and the outer negative electron decreases in strength.
As a result the outer electron will be lost more easily, and so the element will be more reactive.
When sodium reacts with chlorine it forms an ionic salt called ….
sodium chloride.
Some of the compounds formed when alkali metals react with oxygen
Lithium reacts with oxygen to form lithium oxide, Li2O.
Sodium reacts with oxygen to form sodium oxide, Na2O or sodium peroxide, Na2O2.
Potassium reacts with oxygen to form potassium peroxide, K2O2, or potassium superoxide, KO2.