Atomic Structure and the Periodic table Flashcards
What are all substances made of
Atoms
it is the smallest part of an element that can exist
What do atoms have a radius of
0.1 nanometres ( 1x 10-10 m)
What contains almost the whole mass of the atom..
concentrated in the nucleus
What does the nucleus contain
protons and neutrons
What is the radius of the nucleus
1x 10 ^-14
around 1/10,000 of the atom radius
What is the relative mass and charge of the PROTON
relative mass: 1
charge: +1
What is the relative mass and charge of the NEUTRON
relative mass: 1
charge: 0
What is the relative mass and charge of the ELECTRON
relative mass: virtually no mass
charge: -1
Where are electrons in an atom
-move around the nucleus in electron shells
-volume of their orbits determines the size of the atom
Why are atoms neutral and have no charge overall?
-this is bcs they have the same number of protons and electrons
-so the charge is the same of the protons and electrons and cancel eachother out
Why does an ion have an overall charge
-the number of protons does not equal the number of electrons
How many more electrons than protons are there in an ion with a -2 charge
2 more electrons
What does the nucleur symbol of an atom tell u
its atomic proton number and mass number
What does the atomic number (at bottom) tell u
-tells u how many protons there are
What does the mass number (at the top) tell u
the total number of protons and neutrons in the atom
How do u get the number of neutrons
-subtract the atomic number from the mass number
What is an element
is a substance made up of atoms that all have the same number of protons in their nucleus
What determines what type of atom something is
number of protons in the nucelus decides
What is an atom with one proton
hydrogen
What is an atom with two protons
helium
What is a substance that contains atoms with the name number of protons
an element
So different elements..
have atoms with dif number of protons
What are elements represented by
one or two letter symbol
What are Isotopes
-different forms of the same element which have
-the same number of protons but a dif number of neutrons
So what do Isotopes have
Same atomic number
dif mass numbers
What is a v popular pair of isotopes
carbon-12
carbon-13
So compare how many neutrons in Carbon-12 and carbon-13
carbon-12: 6 neutrons
carbon-13: 7 neutrons
As many elements can exist as a number of dif isotopes so what is taken
-relative atomic mass (Ar) instead of mass number
-when refering to the element as a whole
What is relative atomic mass
an average mass taking into account the differnt masses and abundances of all the isotopes that make up the element
How to find Relative Atomic mass (Ar)
=sum of(isotope abundanceX isotope mass number)
divided by
sum of abundances of all the isotopes
What is isotope abundance
a percentage that will be given in the exam
When elements react what happens
-Atoms combine with other atoms to form compounds
What are compounds
are substances formed from two or more elements ,
-the atoms of each are in fixed proportions throughout the compound
-held together by chemical bonds
How do atoms make bonds
making bonds involves atoms giving away,taking or sharing electrons
When atoms make bonds what isn’t affected
-nuclei of the atoms aren’t affected at all when a bond is made
How to seperate a compound
-a chemical reaction
usually difficult to seperate the og elements
What does a compound formed from a metal and non metal consist of
ions
What is ionic bonding
opposite charges of the ions in positive and negative means they are strongly attracted to eachother
How are metal atoms positive (ionic bonding)
they lose electrons to form positive ions
How are nonmetal atoms positive (ionic bonding)
gain electrons to form negative ions
Examples of compounds which are ionically bonded
-sodium chloride
-magnesium oxide
-calcium oxide
What does a compound formed by non metals consist of
consists of molecules
What is covalent bonding
each atom shares an electron with another atom
What are examples of compounds that are bonded covalently
-hydrogen chloride gas
-carbon monoxide
-water
Compare properties of a compound with the original elements
compound usually have totally different properties of the original elements
Compare the mixture of iron and sulfur and the compound formed after heating of iron sulfide
iron(magnetic metal) and sulfur (nice yellow powder)
-compound is a dull grey solid lump and doesn’t behave anything like iron or sulfer
What are compounds represented by
by formulas
What are the formulas made up of
elemental symbols in the same proportions that the elements can be found in the compound
What is carbon dioxide formed from
formed from a chemical reaction between carbon and oxygen
-contains 1 carbon atom and 2 oxygen atoms
CO2
What is the formula of sulfuric acid
H2 SO4
-each molecule contains 2 hydrogen atoms ,1 sulfur atom, 4 oxygen atoms
Formula for calcium hydroxide
Ca(OH)2
1 calcium atom, 2 oxygen atoms, 2 hydrogen atoms
What do the brackets mean in calcium hydroxide Ca(OH)2
little number outside the bracket applies to everything inside the brackets
Formula for Ammonia
NH3
Formula for water
H2 O
Formula for sodium chloride
NaCl
Formula for Carbon monoxide
CO
Formula for hydrochloric acid
HCl
Formula for Calcium chloride
CaCl2
Formula for sodium carbonate
Na2 CO3
What are the 2 different ways to show chemical equations
-Word equation
-Symbol equations
For symbol equations how must it be balanced
must be the same number of atoms on both side
-have to add numbers infront
Difference between a compound or mixture
no chemical bond between different parts of a mixture
What can parts of a mixture be
can be either elements or compounds
How can mixtures be seperated
-seperated by physical methods
eg. Filtration, Crystallisation, simple distillation, fractional distillation, chromotography
What is Air a mixture of
a mixture of gases ,mainly nitrogen,oxygen, carbon dioxide and argon
How easily can gases be seperated
fairly easily
What is crude oil a mixture of
a mixture of different length hydrocarbon molecules
How are properties of a mixture differ to the properties of seperate parts
chemical properties of a substance aren’t affected by it in a mixture
Eg of a mixture with same properties
mixture of iron powder and sulfur powder will contain both properties
-grey magnetic bits of iron and bright yellow sulfur bits
How to seperate dyes
Chromotography
How to seperate insoluble solids from liquids
filtration
What else does filtration can be used with
-in purification
eg. solid impurities seperated out
How to seperate soluble solids from solutions
-Evaporation
-Crystalisation
When do u have to use crystalisation instead of evaporation
-evaporation quick way to seperate soluble salt
-only can use if the salt doesn’t decompose when its heated
-otherwise use crystalisaiton
What can filtration and crystalisation be used for
to seperate rock salt
What is rock salt
a mixture of salt and sand
Why should crystalisation be used
if you want to make nice big crystals of ur salt
How to seperate mixtures which contain liquids
-simple distillation
-fractical distillation
At the start of the 19th centuary what were atoms described as
-John Dalton described atoms as solid spheres and said that dif spheres made up the different elements
What idea did JJ Thomson have in 1897
-weren’t js solid spheres
-Plum pudding model showed the atom as a ball of positive charge with electrons stuck in it
What did Ernest Rutherford do in 1909
-conducted the famous alpha particle scattering experiments
-fired positively charged alpha particles at an extremely thin sheet of gold
What was expected in Ernest Rutherford’s experiment
-expecting the particles to pass straight through the sheet or be slightly deflected at most
Why was this expected in Rutherford’s experiement
-as the positive charge of each atom was thought to be very spread out through the pudding of the atom
What was the results of Rutherford’s experiment
-most particles did go straight through the gold sheet
-some were deflected more than expected
-a small were deflected backwards
What did Rutherford come up with
The Nucleur model of the atom
What was Rutherford’s nucleur model
-tiny positively charged nucleus at the centre, most mass concentrated
-most atom empty space
-surround negative electrons in a ‘cloud’
Why were the atoms deflected (rutherford)
when they came near the concentrated positive charge of the nucleus
Why were the atoms deflected backwards (rutherford)
if they were fired directly at the nucleus
Why did the atoms go straight through (rutherford)
passed through empty space
What did Neil Bohr discover
if the electrons were in a cloud they wld be attracted to the nucelus and cause atom to collapse
What did Neil Bohr propose
that electrons orbit the nucleus in fixed shells
-each shell is fixed distance from the nucleus
What did Further experiments from Rutherford show
-that the nucleus can be divided into smaller particles which each have the same charge as a hydrogen nucleus
-these particles were called protons
Who proved the existence of neutrons
James Chadwick
20yrs after acceptance of nucleus
What did the discovery of neutrons result in
a model of the atom known as the nucleur model
where do electrons occupy
shells
often called energy levels
Which energy levels are first filled with electrons
the lowest ones (closest to the nucleus)
How many electrons are allowed in the 1st shell
2
How many electrons are allowed in the 2nd and 3rd shell each
8 electrons each
What do atoms want (shells)
want full energy shells
What group has already full energy shells
Noble gases in group 0
How were elements catagorised in early 1800s
1.Their weight
2.Their physical and chemical properties
Why was there no such thing as atomic number in early 1800s
as scientists had no idea of atomic structure or of protons,neutrons or electrons
Problems with early periodic tables
-Were not complete
-some elements placed in the wrong groups
-this is bcs they were placed in order or atomic weight and did not take into account their properties
What happened in 1869
Dmitri Mendeleev took 50 known elements and arranged them into his Table of elements
What order did Dmitri put the elements into
-mainly in order of atomic weight
-but moved them if the properties meant it shld be changed
Example of Dmitri switching the order due to properties
-Te and I
-iodine has a smaller atomic weight but is placed after tellurium as it has similar properties to the elements in that group
Why did Dmitri leave gaps in his table
-elements with similar properties stayed in the same groups
-some of the gaps indicated the exsistance of undiscovered elements
-He could predict the properties of unknown ones
When his predictions were proven right what did this mean
helped confirm his ideas and table
give an example of one of his predictions
made good predictions of the chemical and physical properties of an element he called ekasilicon (germanium)
What did the discovery of isotopes in the early 20th centuary confirm
That Mendeleev was correct to not place elements in a strict order of atomic weight but also take account of their properties
What do isotopes of the same element have or not have
-have different masses
-have the same chemical properties
so occupy same position on the periodic table
How many elements are there
100 ish
What is the purpose of the periodic table?
The periodic table helps you to see patterns in properties of elements.
How many elements are there in the periodic table?
There are approximately 100 elements
-which all materials are made of
Where are metals and non-metals located in the periodic table?
Metals are found to the left
non-metals to the right.
What do vertical columns in the periodic table represent?
-Vertical columns are called groups, -elements in the same group have similar properties.
What does the group number indicate?
The group number tells you how many electrons there are in the outer shell.
What is an exception to the group number rule?
Group 0 elements, like Helium, have two electrons in their outer shell.
How can you predict the properties of elements in the same group?
If you know the properties of one element, you can predict properties of other elements in that group.
What trend is observed in reactivity for Group 1 elements?
In Group 1, the elements react more vigorously as you go down the group.
What trend is observed in reactivity for Group 7 elements?
In Group 7, reactivity decreases as you go down the group.
What are the rows in the periodic table called?
The rows are called periods, and each new period represents another full shell of electrons.
How are the elements ordered in the modern periodic table
Order of increasing atomic number
What are metals?
-are elements which can form positive ions when they react
-are located towards the bottom
- to the left of the periodic table.
Where are non-metals located on the periodic table?
Non-metals are at the far right and top of the periodic table.
Do non-metals generally form positive ions?
No, non-metals don’t generally form positive ions when they react.
What affects how atoms will react?
Atoms generally react to form a full outer shell by losing, gaining, or sharing electrons.
Why is it easier for metals to form positive ions?
-Metals to the left of the periodic table have fewer electrons to remove
-those towards the bottom have outer electrons that are further from the nucleus, resulting in weaker attraction.
What is the physical property of metals?
-All metals have metallic bonding so similar properties
-strong
-malleable
-good conductors of heat and electricity
- having high boiling and melting points.
What are the physical properties of non-metals?
- no metallic bonding
-tend to be dull looking
-more brittle
-not always solids at room temperature
-do not generally conduct electricity
-often have a lower density.
What is the difference in bonding between metals and non-metals?
Metals have metallic bonding, while non-metals do not, leading to different physical properties.
What is a consequence of non-metals not having metallic bonding?
Non-metals form a variety of different structures and have a wide range of chemical properties.
Picture of where non metals and metals are on periodic table
Why is it more difficult for non metals to form positive ions by loosing electrons?
-either to the right where they have a lot of electrons to remove to get a full outer shell
-or towards top where outer electrons close to nucleus so a strong attraction
What is more feasible for metals to do
The elements to react to form positive ions with a full outer shell
-so not much energy is needed to remove electrons
What is more feasible for non metals to do
For them to either share or gain electrons to get a full outer shell
What are Group 1 elements known as?
the alkali metals.
What are the alkali metals?
The alkali metals are lithium, sodium, potassium, rubidium, caesium, and francium.
What is a characteristic of alkali metals regarding their outer shell?
all have one electron in their outer shell, making them very reactive and gives them similar properties
What are the physical properties of alkali metals?
The alkali metals are all soft and have low density.
What are the trends for alkali metals as you go down Group 1?
1) Increasing reactivity
2) Lower melting and boiling points. 3) Higher relative atomic mass.
How do alkali metals form ionic compounds?
The Group 1 elements readily lose their one outer electron to form I+ ions.
Don’t need much energy
What do alkali metals produce when they react with water?
They produce hydrogen gas and form hydroxides that dissolve in water to give alkaline solutions.
What happens when Group 1 metals react with water?
They react very vigorously
- more reactive metals(lower down) having more violent reactions.
What is the reaction of sodium with water?
sodium + water → sodium hydroxide + hydrogen
What do alkali metals produce when they react with chlorine gas
React vigorously
They form white salts called metal chlorides
As u go down group , more vigorous
What is the reaction of sodium with chlorine?
2Na + Cl2 → 2NaCl
Sodium+chlorine—>sodium chloride
What do Group 1 metals form when they react with oxygen?
They form metal oxides.
What happens to alkali metals in air?
They tarnish in the air, forming a dull metal oxide layer.
What oxide does lithium form when reacting with oxygen?
Lithium reacts to form lithium oxide (Li2O).
What oxides does sodium form when reacting with oxygen?
Sodium reacts to form a mixture of sodium oxide (Na2O) and sodium peroxide (Na2O2).
What oxides does potassium form when reacting with oxygen?
Potassium reacts to form a mixture of potassium peroxide (K2O2) and potassium superoxide (KO2).
Why does group 1 increase in reactivity as it goes down
-The outer electron is more easily lost as the attraction between the nucleus and electron decreases
- as the electron is further away from the nucleus the further down
What do alkali metal ionic compounds with non metals look like
Generally white solids that dissolve in water to form colourless solutions
How do Lithium , sodium and potassium react with water
Float and move around the surface , fizzing furiously
-potassium can ignite hydrogen
What are the Group 7 elements commonly known as?
The Group 7 elements are known as the halogens.
What are the physical states of halogens?
Halogens are all non-metals with coloured vapours.
What is the state and color of Fluorine?
Fluorine is a very reactive, poisonous yellow gas.
What is the state and color of Chlorine?
Chlorine is a fairly reactive, poisonous dense green gas.
What is the state and color of Bromine?
Bromine is a dense, poisonous, red-brown volatile liquid.
What is the state and color of Iodine?
Iodine is a dark grey crystalline solid or a purple vapour.
How do halogens exist?
They all exist as molecules which are pairs of atoms.
What happens to reactivity as you go down Group 7?
Halogens become less reactive as you go down Group 7.
What happens to melting and boiling points as you go down Group 7?
Melting and boiling points increase as you go down Group 7.
What happens to relative atomic masses as you go down Group 7?
Relative atomic masses increase as you go down Group 7.
What is a trend you can predict about iodine compared to chlorine?
Iodine will have a higher boiling point than chlorine.
Why do all Group 7 elements react in similar ways?
They all have seven electrons in their outer shell.
How do halogens form molecular compounds?
Halogen atoms can share electrons via covalent bonding with other non-metals to get a full outer shell
What are examples of compounds that contain covalent bonds with halogens and non metals?
Examples include HCl, PCl5, HF, and CCl4.
What type of ions do halogens form when they bond with metals?
Halogens form 1- ions called halides (F-, Cl-, Br-, and I-).
What type of structures do compounds formed by halogens and metals have?
The compounds have ionic structures.
What can a more reactive halogen do in a displacement reaction?
A more reactive halogen can displace a less reactive one from its salt.
Give an example of a displacement reaction involving halogens.
-Chlorine can displace bromine and iodine from their aqueous solutions.
-Bromine will also displace iodine due to reactivity trend
Name me the 4 Halogens
-Fluorine
-Chlorine
-Bromine
-Iodine
What does ionic bonding look like between halogens and metals
What are Group 0 elements commonly known as?
noble gases.
What are the characteristics of noble gases?
-so energetically stable
-means they are mostly inert and won’t move react with much at all
Which elements are included in Group 0?
Group 0 elements include helium, neon, argon, krypton, xenon, and radon.
How many electrons do noble gases have in their outer energy level?
They all have eight electrons in their outer energy level
except helium, which has two.
What state do Group 0 elements exist in?
They exist as monatomic gases, meaning single atoms not bonded to each other.
-colourless gases at room temp
What is the flammability of noble gases?
Noble gases are non-flammable; they won’t set on fire.
What happens to the boiling points of noble gases as you move down the group?
The boiling points increase increasing relative atomic mass.
What causes the increase in boiling points of noble gases?
due to an increase in the number of electrons in each atom
, leading to greater intermolecular forces between them which need to be overcome
How can you estimate the boiling point of a noble gas?
You can estimate it by knowing the boiling point of another noble gas in the group.
What is the predicted state of helium at 25 °C if neon is a gas at that temperature?
Helium must also be a gas at 25 °C since it has a lower boiling point than neon.
What is the predicted boiling point of xenon if radon and krypton have boiling points of -62 °C and -153 °C respectively?
Xenon’s boiling point would be about -108 °C, halfway between radon and krypton.
