Atomic Structure and the Periodic Table(1) Flashcards
What is an atom
An atom is the smallest part of an element that can exist
What is an element?
An element is a substance of only one type of atom.
How are the elements listed and approximately how many are there?
They are listed in the periodic table; there are approximately 100.
Elements can be classified into two groups based on their properties; what are these
groups?
Metals and non-metals
What is a compound?
Two or more elements combined chemically in fixed proportions which can be represented by formulae
Do compounds have the same properties as their constituent elements?
No, they have different properties.
What is a mixture? Does it have the same chemical properties as its
constituent materials?
A mixture consists of two or more elements not chemically combined together; it does have the same chemical properties
What are the methods through
which mixtures can be separated (there are 6)? Do these involve chemical reactions?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography; they do not involve chemical reactions
Describe and explain simple distillation in steps
Step 1
Step1
Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser.
Describe and explain simple distillation.
Step 2
Step 2
The thermometer will read the boiling point of the pure liquid.
Describe the difference between simple distillation and evaparation
Simple distillation keeps the liquids where as evaporation doesn’t
Describe and explain evaporation
Evaporation is a technique for separation of a solid dissolved in a solvent from a solvent (e.g. salt from H(small2)O)
The solution is heated until all the solvent evaporates; the solids stays in the vessel.
Describe and explain Crystallisation
Crystallisation is similar to evaparation ,
but we only remove some of the solvent by evaporation to form a saturated solution (the one where no more solid can be dissolved). Then, we cool down the solution.
As we do it, the solid starts to crystallise, as it becomes less soluble at lower temperatures.
The crystals can be collected and separated from the solvent via filtration.
What is a solvent
A solvent is the term used for the liquid in which a substance (solute) is dissolved
What is a solute
A solute is a solid, liquid, or gas which is dissolved to make a solution
What is a solution
A solution is a homogeneous(similar) of one or more solutes dissolved in a solvent
Describe and explain fractional distillation
Fractional distillation is a technique for separation of a mixture of liquids. It works when liquids have different boiling points.
What makes the apparatus of a simple distillation different to a fractional distillation
It has an addittional fractionating column placed on top of the heated flask
What does the fractionating column contain and whats its purpose
It contains glass beads which help to separate the compounds
What happens in industry in fractional distillation
mixtures are repeatedly condensed and vapourised. The column is hot at the bottom and cold at the top. The liquids will condense at different heights of the column
Describe and explain filtration
3 steps
Filtration is used to separate an insoluble solid suspended in a liquid.
The insoluble solid (called a residue) gets caught in the filter paper, because the particles are too big to fit through the holes in the paper.
The filtrate is the substance that comes through the filter paper.
What is the apparatus used in filtration
filter paper + funnel.
Describe and explain chromatography
Chromatography is used to separate a mixture of substances dissolved in a solvent.
Explain paper Chromatography in steps
Step 1
Step1
place a piece of paper with a spot containing a mixture in a beaker with some solvent
Explain paper Chromatography in steps
Step 2
Step 2
The bottom of the paper has to be in contact with the solvent.
Explain paper Chromatography in steps
Step 3
The solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components).
What is a separating funnel?
A separatory funnel is an apparatus for separating immiscible ( can’t mix) liquids.
What is a immiscible liquid
Immiscible liquids are those which won’t mix to give a single phase
Eg oil and water
What will two immiscible liquids of different densities form in a funnel
Two distinct layers in the separatory funnel
In a separating funnel what can you do to the bottom layer (the liquid with a greater density)
You can run off the bottom layer to a separate vessel
.
.
Describe the plum-pudding model
The atom is a ball of positive charge with negative electron embedded in it.
Describe the Bohr/nuclear model
The nuclear model suggests that electrons orbit the nucleus at specific distances (shells)
How did the bohr/nuclear model come about
it came about from the alpha scattering experiments
Later experiments led to the discovery of smaller, positive
particles in the nucleus; what are these particles called?
Protons
What did the work of James Chadwick provide evidence
for?
The existence of neutrons in the nucleus
Describe the structure of an atom
The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons
State the relative masses and relative charges of the proton,
neutron and electron
Proton Mass 1 Charge +1
Neutron Mass 1 Charge 0
Electron Mass 1/2000 Charge -1
Explain why atoms are electrically neutral.
They have the same number of electrons and protons
What is the radius of an atom?
0.1 nm
What is the radius of an atom?
0.1 nm
What is the radius of a nucleus and what is it compared to that of the atom?
the radius of an atom is about 0.1 nm (1 × 10-10 m)
the radius of a nucleus (1 × 10-14 m) is less than 110 , 000 of the radius of an atom
What name is given to the number of protons in the
nucleus?
Atomic number
Atoms of the same element have the same number of which particle
in the nucleus?
Protons
Where is the majority of mass of an atom?
The nucleus
What is the mass number?
The total number of protons and neutrons
How does one calculate the number of neutrons using mass
number and atomic number?
Subtract the atomic number from the mass number
What is an isotope?
Atoms of the same element have the same number of proton but have a different number of neutrons.
Do isotopes
of a certain element have the same chemical properties?
They have the same chemical properties as they have the same electronic structure
What is the relative atomic mass?
The average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where the mass of 12(small)C is 12.
Give the electronic configurations of He (2), Be (4), F (9), Na (11), and Ca
(20) to demonstrate how shells are occupied by electrons.
2 (He)
2,2 (Be)
2,7(F)
2,8,1(Na)
2,8,8,2 (Ca)
What are ions?
Ions are charged particles. They are formed when atoms lose electrons (positive ions) or gain (negative ions) electrons.
E.g. sodium positive ion, Na+, has an electronic configuration of 2,8 (same as Ne). An atom of sodium has lost one electron.
What is the Boiling/meting point of metals
High
What can metals conduct
Heat and electricity
What is the apparence if metals
Shiny
Are metals malleable
Yes
What is the density of metals
High
What is the oxcidity of metals
Basic
What is the oxcidity of metals
Basic
What is the boiling point /melting point of non metals
Low
.
.
What is the conductvity of non metals
Don’t conduct heat, electricity (with exception of graphite)
What is the appearance of non metals
Dull
What is the Malleability of non metals
Brittle
What is the density of non metals
Low
What is the oxcidity of non metals
Acidic
What is formed when a metal reacts with a
non-metal?
An ionic compound (made of positive and negative ions).
What is formed when a non-metal reacts with a
non-metal?
A molecular compound containing covalently bonded atoms.
What is Miscible
Miscible refers to the substances (particularly liquids) that mix together, e.g. water and alcohol.
The columns of the periodic table are called…?
Groups
The rows of the periodic table are called…?
Periods
Are elements in the same group similar or different?
They may have similar chemical properties, as they have the same number of outer shell electrons.
In terms of energy levels, what is the same between elements of the same period?
They have the same number of energy levels
Electrons occupy particular energy levels, with each electron in an atom at a
particular energy level; which available energy level do electrons occupy?
The lowest available energy level
The elements of Group 0 are more commonly known
as…?
The noble gases
What makes the periodic table periodic?
Similar properties of elements occur at regular intervals
Elements in the same group have the
same number of electrons in their outer shell; what does this tell us about their chemical properties?
They have similar chemical properties
In terms of shells, what is the difference between elements in the same period?
The number of electron. shells is therefore the same across a period but increases when moving down a group.
What change in shell number is seen as one moves down a group?
The number of shells increases
Early periodic tables were
incomplete and elements were placed in inappropriate groups if what was to be followed?
The strict order of atomic weights
Knowledge of what made it possible to explain why the order
based on atomic weights was not always correct?
Isotopes
Mendeleev overcame some problems with the table by doing
what? He also changed the order of some elements based on what?
Leaving gaps; atomic weights
The majority of elements are…?
Metals
Elements that react to form positive ions are…?
Metals
Elements that do not form positive ions are…?
Non-metals
(Anions)
Elements in Group 1 are known as…?
The alkali metals
State 4 characteristics of the Alkali Metals
All have one electron in their outer shell
have low density
are stored under oil (to prevent reactions with oxygen or water)
are soft (can be cut with knife).
How do Group 1 elements react with non-metals? Why are these reactions similar for the different
Group 1 elements?
They form ionic compounds which are soluble white solids which form colourless solutions – they all have one electron in their outer shell.
How do Group 1 elements react with water?
They release hydrogen and form hydroxides which dissolve to form alkaline solutions; react vigorously with water fizzing and moving around on the surface of the water.
How does the reactivity change moving down Group 1? Why?
3 reasons
Reactivity increases as the atoms get larger
the distance between the nucleus and the outer electrons increases
attraction from the nucleus decreases allowing atoms to more easily lose electrons.
State five characteristics of Group 7
- 7 electrons in outer shell
- Coloured vapours
- Diatomic molecules
- Form ionic salts with metals
- Form molecular compounds with non-metals
State the names of all the group 7 elements
Fluorine (F Fsmall 2)
Chlorine (Cl Cl small 2)
Bromine (Br Br small 2)
Iodine (I I small 2)
What does fluorine look like
A pale yellow gas
What does Chlorine look like
A pale green gas
What does Bromine look like
A dark brown liquid
What does Iodine look like
A grey soild
What does Iodine look like
A grey soild
State three changes that occur in Group 7 as one moves down the group
- Higher relative molecular mass
- Higher melting and boiling point
- Less reactive – less easily gain electrons
A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; write the
equations and state the colour change seen when chlorine reacts with sodium bromide and when chlorine/bromine reacts with sodium iodide.
Cl(small 2) + 2 NaBr → Br2 + 2 NaCl, or Cl2 + 2Br– → Br(small 2)+ 2 Cl–;
in this reaction, an orange colour of Br(small 2) would appear
C(small 2) + 2 NaI → I(small 2)+ 2 NaCl, or Cl(small 2)+ 2I– → I(small 2)+ 2 Cl– Br(small 2)+ 2 NaI → I(small 2)+ 2 NaBr, or Br(small 2)+ 2I– → I(small 2)+ 2 Br–;
in these two reactions, a brown colour of I2 would appear
A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; explain the
trend in reactivity of halogens in these reactions
Reactivity decreases down the group. As we go down the group, the atoms get larger, so an incoming electron will be less tightly held by the attractive forces from the nucleus. That’s why Cl(small 2) displaces Br– and I–.
Compare Group 1 metals and transition metals
Group 1 metals and transition metals are heat and electricity conductors. They are shiny when polished and form ionic compounds with non metals.
Transition metals have higher densities and higher melting points than Group 1 metals. They are less reactive and harder than Group 1 metals.
Compare Group 1 metals and transition metals
Group 1 metals and transition metals are heat and electricity conductors. They are shiny when polished and form ionic compounds with non metals.
Transition metals have higher densities and higher melting points than Group 1 metals. They are less reactive and harder than Group 1 metals.
State three common characteristics of transition metals
- Ions with different charges
- Coloured compounds
- Catalytic properties
.
.
What is a catalyst?
A catalyst is a chemical substance that increases the rate of a chemical reaction.
It is not used up over the course of the reaction.
It also speeds up the rate of reaction by providing an alternate lower energy reaction pathway and is regenerated
State the colour of flames observed when lithium burn in oxygen
Crimson-red, Li
State the colour of flames observed when sodium burn in oxygen
Yellow-orange, Na
State the colour of flames observed when potassium burn in oxygen
Lilac, K
Describe the properties of noble gases.
Non-metals, gases, low boiling points, unreactive (full outer shell; they don’t easily accept or lose electrons).
Discuss the trend in boiling/melting point down the group 7
The boiling point increases down the group, as the atoms get heavier.
Discuss the trend in boiling point down group 7
The boiling point increases down the group, as the atoms get heavier.
What are the diatomics
are molecules composed of only two atoms, of the same or different chemical elements.
hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), and iodine (I)
What is a homogeneous mixture
A homogeneous mixture is one that’s mixed or blended together so well that all of the ingredients will not separate out, even over time
