C1 Atomic Structure 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
Elements may combine through chemical reactions to form new products; what are these new substances called?
Compounds
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 or compounds not chemically combined together; hit does have the same chemical properties
What are the methods through which mixtures can be separated (there are five)? Do these involve
chemical reactions?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography; they do not involve chemical reactions
Describe and explain simple distillation.
Simple distillation is used to separate liquid from a solution - the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid. Contrary to evaporation, we get to keep the
liquid.
Describe and explain crystallisation/evaporation
Evaporation is a technique for separation of a solid dissolved in a solvent from a solvent (e.g. salt from H20).
The solution is heated until al the solvent evaporates; the solids stays in the vessel.
Crystallisation is similar, 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 ti becomes less soluble at lower temperatures. The crystals can be collected and separated from the solvent via filtration.
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.
The apparatus is similar to the one of simple distillation apparatus, with the additional fractionating column placed on top of the heated flask.
The fractionating column contains glass beads. It helps to separate the compounds. In industry, mixtures are repeatedly condensed and vaporised. 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
Filtration is used to separate an insoluble solid is 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.
Apparatus: filter paper + tunnel
Describe and explain chromatography
Chromatography is used to separate a mixture of substances dissolved in a solvent.
In paper chromatography, we place a piece of paper with a spot containing a mixture in a beaker with some solvent. The bottom of the paper has to be in contact with the solvent. 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 liquids. Two immiscible liquids of different densities will form two distinct layers in the separator funnel.
We can run off the bottom layer (the liquid with greater density) 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 and how it came about
The nuclear model suggests that electrons orbit the nucleus at specific distances (shells) - 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 = very small, charge = -1 (respectively)
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 a nucleus and what is it compared to that of the atom?
1×10-14mand 1/10000
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? Do isotopes of a certain element have the same chemical properties?
Atoms of the same element (same proton number) that have a different number of neutrons.
They have the same chemical properties as they have the same
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 12C (Carbon-12) 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.
He, Be, F, Na, Ca configurations (respectively):
2
2,2
2,7
2,8,1
2,8,8,2
What are ions?
Ions are charged particles. They are formed the atoms lose electros (positive ions) or gain (negative ions) electrons.
E.g. sodium positive ion, Na+, has an electronic configuration of 2,8 ( same as Ne). Ann atom of sodium has lost one electron.
Compare the properties of metals and non-metals
Metals
High - Boiling/meting point
Heat and electricity - Conductivity
Shiny - Appearance
Yes - Malleability
High - Density
Basic - Oxides
Non-metals
Low - Boiling/meting point
Don’t conduct heat, electricity (with the exception of graphite) - Conductivity
Dull - Appearance
Brittle - Malleability
Low - Density
Acidic - Oxides
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.
Atoms share electrons, as opposed to transferring electrons between each other (cf. ionic compounds).
Explain the following: solute, solvent, solution, miscible, immiscible, soluble, insoluble.
A solute is a substance that is dissolved in a solvent. Together, they form a solution.
Miscible refers to the substances (particularly liquids) that mix together, e.g. water and alcohol. Water and oil are immiscible, i.e. they do not mix.
Soluble refers to the substance that can be dissolved ni a solvent, e.g. salt ni water. Insoluble substances won’t dissolve in a particular solvent.
The columns of the periodic table are called..?
Groups
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.
The rows of the periodic table are called..?
Periods
In terms of energy levels, what are the differences between elements of the same period?
They have the same number of energy levels
Electrons occupy particular energy levels, with each
electron ni 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 ni their outer shell; what
does this tell us about their chemical properties?
They have similar chemical properties
In terms of shells, what si the difference between elements ni the same period?
They have the same number of shells
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 fi
what was to be followed?
The strict order of atomic weights
Knowledge of what made ti 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
Elements in Group 1are known as..?
The alkali metals
State three 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 1elements react with non-metals? Why are these reactions similar for the different Group 1elements?
They form ionic compounds which are soluble white solids which form colourless solutions - they al 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 reactivity change moving down Group 1? Why?
Reactivity increases as the atoms get larger and the distance between the nucleus and the outer electrons increases and thus attraction from the nucleus decreases, allowing them 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 five State Group 7 elements and states of matter of molecules they form
- Fluorine, F, F2 is a pale yellow gas
- Chlorine, Cl, Cl2 is a pale green gas
- Bromine, Br, Br2 is dark brown liquid
- Iodine, I, I2 is a grey solid
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, +2NaBr →Br, +2NaCl, or
Cl+2Br →Br, +2Cl;
in this reaction, na orange colour of Br, would appear
C12+2Nal →21+2NaCl,roCl+12 →21+2Cr
Br, +2Nal →21+2NaBr, or Br, +21 →12+ 2Br;
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 ni 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 Cl2 displaces Br- and I-
Compare group 1metals with 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 1metals. They are less reactive and harder than Group 1metals.
State three common characteristics of transition metals
- lons 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.
State the colours of flames observed when lithium, sodium, and potassium burn in oxygen
Crimson-red, Li
Yelow-orange, Na
Lilac, K
Describe the properties of noble gases. Discuss the trends in properties down the group.
Non-metals, gases, low boiling points, unreactive (full outer shell; they don’t easily accept or lose electrons).
The boiling point increases down the group, as the atoms get heavier.
Alkali metals:
The elements in Group 1 of the periodic table.
Atom:
The smallest part of an element that can exist. All substances are made up of atoms.
Atomic nucleus:
Positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it.
Atomic number:
The number of protons in the nucleus.
Chromatography:
A separation technique used to separate a mixture of chemicals by distributing the components between two phases.
Compound:
A substance made up of two or more types of atoms chemically combined together.
Crystallisation:
A separation technique used to produce solid crystals from a solution by evaporating the solvent.
Displacement:
A chemical reaction in which a more reactive element displaces a less reactive element from its compound.
Electron:
Negatively charged subatomic particle which orbit the nucleus at various energy levels. Very small relative mass (negligible).
Electron shell:
Different energy levels in atoms occupied by electrons.
Element:
A substance made up of only one type of atom.
Filtration:
A separation technique used to separate solids from liquids.
Fractional distillation:
A method of separating a mixture of substances according to their different boiling points.
Group (periodic table):
The columns of the periodic table represent different groups of elements. Elements with similar properties are in the same group.
Halogens:
The elements in Group 7 of the periodic table.
Ion:
An atom or molecule with an electric charge due to the loss or gain of electrons.
Isotope:
Atoms of the same element with the same number of protons but a different number of neutrons.
Mass number:
The total number of protons and neutrons in the nucleus.
Metals:
Elements that react to form positive ions. Found to the left and towards the bottom of
the periodic table.
Mixture:
A mixture consists of two or more elements or compounds not chemically combined together.
Neutron:
Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1.
Noble gases:
The elements in Group 0 of the periodic table.
Non-metals:
Elements that react to form negative ions. Found towards the right and top of the periodic table.
Nuclear model:
The nuclear atomic model stated that the mass was concentrated at the centre of the atom and that the nucleus was charged.
Periodic table:
Table of elements arranged in order of atomic number and such that elements with similar properties are in the same column (group).
Plum pudding model:
Atomic model devised after the discovery of the electron. The model suggests the atom is a ball of positive charge with negative electrons scattered through it.
Proton:
Positively charged subatomic particle present in the nucleus of the atom. Relative mass of 1.
Relative atomic mass:
An average value that takes account of the abundance of the isotopes of the element.
Simple distillation:
A procedure by which two liquids with different boiling points can be separated.
Transition metals:
The collection of metallic elements in the middle of the periodic table.
