Atomic Structure And The Periodic Table Flashcards
What is an atom?
the smallest particle of an element that can exist
What is an element?
a substance that contains 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 are compounds?
Materials made of the atoms of two or more different elements, which have chemically combined.
Do compounds have the same properties as their constituent elements?
No, they have different properties
What is a mixture?
material composed of two or more elements or compounds that are physically mixed together but not chemically combined (it does have the same chemical properties)
What are the methods through which mixture can be separated?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography (they don’t 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
- crystallisation is similar to evaporation
- 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 in 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 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
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 + funnel.
Describe and explain chromatography
Chromatography is used to separate a mixture of substances 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 separatory funnel. We can run off the bottom layer (the liquid with greater density) to a separate vessel.
Describe the plum pudding model
The plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it
Describe the Bohr model
-single electron circled around nucleus in orbits
-each orbit had a specific energy
-orbits closer to nucleus = lower energy
-lots of empty space between nucleus and electron
(It came about from the alpha scattering experiments)
What is a proton?
positively charged particle found in the nucleus
What is a neutron?
a particle that has no charge and that is inside the nucleus
What is an electron?
a negatively charged subatomic particle
What did 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 charges of the subatomic particles
Protons: +1, neutrons: 0, electrons: -1
State the relative masses of subatomic particles
Protons: 1, neutrons: 1, electrons: 1/1835
Explain why atoms are electrically neutral.
They have the same number of electrons and protons
What is the radius of an atom?
0.1 nanometers
What is the radius of a nucleus and what is it compared to that of the atom?
1 x 10-14 m and 1/10000
What is the atomic number?
the number of protons in an atom
Where is the majority of mass of an atom?
nucleus
What is the mass number?
the total number of protons and neutrons in a nucleus.
How does one calculate the number of neutrons using mass number and atomic number?
mass number - atomic number
What is an isotope?
Atoms of the same element that have different numbers of neutrons but the same number of protons
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 relative atomic mass?
An average mass of isotopes making up an element and how much of each element there is.
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.
Compare the properties of metals and non-metals
Metals: High boiling and melting point, conduct heat and electricity, shiny, malleable, high density, basic oxides.
Non metals: low boiling and melting point, don’t conduct heat and electricity except graphite, dull, brittle, 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).
What is a solute?
the substance that is dissolved
What is a solvent?
the substance in which the solute dissolves
What is a solution?
a mixture of solute and solvent
What is miscible?
two liquids that are soluble in each other
What is immiscible?
liquids that are insoluble in one another
What is soluble?
capable of being dissolved
What is insoluble?
incapable of being dissolved
What are groups?
Vertical columns on the periodic table
What are periods?
Horizontal rows on the periodic table
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 are the differences between elements of the same period?
They have the same number of energy levels
Which available energy level do electrons occupy?
The lowest available energy level
What are group 0 known as?
noble gases
What makes the periodic table periodic?
Similar properties of elements occur at regular intervals
In terms of shells, what is the difference between elements in 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
Why was the order based on atomic weights 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
What are the majority of elements?
metals
What are elements that react to form positive ions?
metals
What are elements that don’t form positive ions?
Non- metals
What the elements in group 1 known as?
The alkali
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 1 elements react with non-metals?
They form ionic compounds which are soluble white solids which form colourless solutions
How do group 1 metals 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?
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 Group 7 elements and their states of matter.
- 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
State three common characteristics of transition metals
- Ions with different charges
- Coloured compounds
- Catalytic properties
What is a catalyst?
A catalyst is a substrate which increases the speed of a reaction without being changed or used up in the reaction. It is not used up over the corse of the reaction
Describe the properties of noble gases. Discuss the trend in boiling point 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.
State the colours of flames observed when lithium, sodium, and potassium burn in oxygen
Li - crimson red
Na - yellow-orange
K - lilac
What are neutral atoms?
Same number of positive protons as negative electrons
What are energy levels/electrons shells?
The region surrounding the nucleus where electrons orbit the nucleus
What can the first shell hold?
2 electrons
What can the rest of the shells (excluding one) hold?
8 electrons
What are valence electron?
Outer shell electrons which are involved in reactions
What is saturated?
A solution that cannot dissolve any more solute at a given temperature
What is a chemical reaction?
The formation of a new chemical substance
What are the name of group 7?
The halogens
What is a diatomic molecule?
A molecule consisting of two atoms
What is a displacement reaction?
A reaction in which a more reactive element replaces a solider element in a compound
Where are transition metals found?
In the middle of the periodic table
What are the physical properties of transition metals?
High melting points (strong covalent bonds), high density, malleable, ductile, shiny, conducts electricity and heat
What are the chemical properties of transition metals?
Form coloured compounds, tend to be catalysts and variable oxidation states
What are the charges of transition metal ions?
Form positive ions often with the ability to form more than one ion
What are the most reactive metals?
Potassium, sodium, calcium, magnesium, aluminium and carbon
What are the least reactive metals?
Platinum, gold, silver, copper, hydrogen, lead, tin, iron and zinc
What is the equation for metals with water?
Metal + water —> metal hydroxide + hydrogen
What is the equation for metals with acids?
Metal + acid —> salt + hydrogen
What is an example for a reaction for metals with water?
Calcium + water —> hydroxide + hydrogen
What is an example for a reaction for metals with acids?
Magnesium + Hydrochloric acid —> magnesium chloride + hydrogen
What is the name for group 1 elements?
Alkali metals
What is the pattern of reactivity down group 1?
Reactivity increases
What are the properties of group 1 elements?
- low density -> which decreases down group 1
- good conductors if heat and electricity
- shiny when cut, but tarnish as they react with oxygen
What are the properties of group 0 elements?
- stable share of electrons -> unreactive
- boiling points increase as you go down the group
- colourless gasses at room temperature
What does inert mean?
Very unreactive
What are metals?
Elements which form positive ions
What are non-metals?
Elements which don’t form positive ions
Where is the metals position on the periodic table?
On the left hand side
Where is the non-metal position on the periodic table?
On the right hand side
What was John Newland’s idea about periodic table?
Noticed a repeating pattern every 8 element and suggested elements were found in ‘octaves’
What was the order of elements on the historic periodic table?
Elements were ordered by atomic weight
What is the order of elements on modern periodic table?
Elements are ordered by atomic number
What was Dmitri Mendeleev’s idea about the periodic table?
Ordered elements by atomic weight but changed the order/left gaps to keep elects with silica properties in the same column
What was the advantage of Mendeleev’s idea about the periodic table?
He was able to predict the properties of elements in the gaps
