Atomic Structure and the Periodic Table Flashcards
What is an atom?
smallest part of an element that can exist
What is an element?
a substance made of only one type of atom
Where are elements listed and approximately how many are there?
- listed in periodic table
- approximately 100
Elements can be classified into 2 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?
2 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
What is a mixture?
2 or more elements or compounds not chemically combined together
Do mixtures have the same properties as their constituent elements?
yes
What are 5 methods through which mixtures can be separated? Do they involve chemical reactions?
- filtration
- crystallisation
- simple distillation
- fractional distillation
- chromatography
they do not involve chemical reactions
Describe and explain simple distillation
- used to seperate liquid from a solution
- liquid boils off and condenses in the condenser
- 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 separates a solid dissolved in a solvent from a solvent
- solution heated until all solvent evaporates, solid stays in vessel
- crystallisation is similar, but only some of the solvent is removed by evaporation to form a saturated solution
- the solid starts to crystallise as it becomes less soluble at lower temperatures
- crystals can be collected and separated from the solvent via filtration
Describe and explain fractional distillation
- separating a mixture of liquids where the liquids have different boiling points
- apparatus similar to simple distillation, with an additional fractionating column on top of the heated flask - fractionating column contains glass beads to help separate the compounds
- in industry, mixtures are repeatedly condensed and vapourised
- column is hot at bottom and cold at top
- liquids condense at different heights of the column
Describe and explain filtration
- used to separate insoluble solid suspended in a liquid
- residue gets caught in filter paper (particles too big to fit through holes in paper)
- filtrate is the substance that comes through the filter paper
- apparatus: filter paper & funnel
Describe and explain chromatography
- separate mixture of substances dissolved in a solvent
- paper chromatography: paper with a spot containing a mixture in a beaker with some solvent, bottom of paper must be in contact with the solvent, solvent level will start to rise, thus separating the spot (mixture) into few spots (components)
What is a separating funnel?
- apparatus for separating immiscible liquids
- 2 immiscible liquids of different densities will form 2 distinct layers in the separatory funnel
- we can run off the bottom layer (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 & 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
masses - 1, 1, very small
charges - 1, 0, -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 a nucleus and what is it compared to that of an atom?
1 x 10^-14m and 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?
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 (same proton number) that have a different number of neutrons
Do isotopes of a certain element have the same chemical properties?
they have the same chemical properties because 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 C(12) is 12
Give the electronic configuration of He (2) to demonstrate how shells are occupied by electrons
2
Give the electronic configuration of Be (4) to demonstrate how shells are occupied by electrons
2,2
Give the electronic configuration of F (9) to demonstrate how shells are occupied by electrons
2,7
Give the electronic configuration of Na (11) to demonstrate how shells are occupied by electrons
2,8,1
Give the electronic configuration of Ca (20) to demonstrate how shells are occupied by electrons
2,8,8,2
What are ions?
charged particles, formed when atoms lose/gain electrons
Compare the boiling/melting point of metals and non-metals
metals; high
n-m; low
Compare the conductivity of metals and non-metals
metals; heat & electricity
n-m; don’y conduct heat/electricity (with the exception of graphite)
Compare the appearance of metals and non-metals
metals; shiny
n-m; dull
Compare the malleability of metals and non-metals
metals; yes
n-m; brittle
Compare the density of metals and non-metals
metals; high
n-m; low
Compare the oxides of metals and non-metals
metals; basic
n-m; acidic
What is formed when a metal reacts with a non-metal?
an ionic compound
What is formed when a non-metal reacts with another non-metal?
a molecular compound containing covalently bonded atoms
atoms share electrons, as opposed to transferring electrons between each other
Explain the following terms: solute, solvent, solution, miscible, immiscible, soluble, insoluble
solute - substance dissolved in solvent, together they form a solution
miscible refers to the substances (particularly liquids) that mix together
immiscible substances don’t mix (like water and oil)
soluble refers to the substance that can be dissolved in a solvent (like salt in water)
insoluble substance won’t dissolve in a particular solvent
What are the columns of the periodic table called?
groups
What are the rows of the periodic table called?
periods
Why are elements in the same group similar?
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
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
What are the Group 0 elements more commonly known as?
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 are similar
In terms of shells, what’s the difference between elements in the same period?
same number of shells, different number of outer shell electrons
What change in shell number is seen as one moves down a group?
increases
Early periodic tables were incomplete and elements were placed in inappropriate groups because they were organised how?
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?
leaving gaps
Mendeleev changed the order of some elements based on what?
atomic weights
Are the majority of elements metals or non-metals?
metals
Do metals react to form positive or negative ions?
positive ions
Do non-metals react to form positive or negative ions?
negative ions
What are elements in Group 1 known as?
alkali metals
State 3 characteristics of alkali metals
- one electron in their outer shell
- stored under oil (prevent reactions with oxygen or water)
- soft (can be cut with a knife)
How do Group 1 elements react with n-m? Why are these reactions similar for the different Group 1 elements?
- form ionic compounds which are soluble white solids which form colourless solutions
- all have 1 electron in their outer shell
How to G1 elements react with water?
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 G1? Why?
- reactivity increases
- atoms get larger & 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 5 characteristics of Group 7
- 7 electrons in outer shell
- coloured vapours
- diatomic molecules (any chemical compound that is made up of only two atoms)
- form ionic salts with metals
- form molecular compounds with n-m
State 4 G7 elements & their states of matter
- Fluorine (F), pale yellow gas
- Chlorine (Cl), pale green gas
- Bromine (Br), dark brown liquid
- Iodine (I), grey solid
State 3 changes that occur in G7 as one moves down the group
- higher relative molecular mass
- higher melting & boiling points
- less reactive - less easily gain electrons
A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; write the equation and state the colour change seen when chlorine reacts with sodium bromide
Cl2 + 2NaBr –> Br2 + 2NaCl
or
Cl2 + 2Br- –> Br2 + 2Cl-
in this reaction, an orange colour of Br2 would appear
A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; write the equation and state the colour change seen when chlorine/bromine reacts with sodium iodide
Cl2 + 2NaI –> I2 + 2NaCl
or
Cl2 + 2I- –> I2 + 2Cl-
(bromine has same equation, but with Br in place of Cl)
in both 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, atoms get larger, so an incoming electron will be held less tightly by attractive forces from the nucleus
- that’s why Cl2 displaces Br- and I-
Compare G1 metals and transition metals
- both are heat & electricity conductors
- both are shiny when polished
- both form ionic compounds with n-m
-transition have higher densities & higher melting points
- transition are less reactive and harder
State 3 common characteristics of transition metals
- ions with different charges
- coloured compounds
- catalytic properties
What is a catalyst?
chemical substance that increases the rate of a chemical reaction, is not used up over the course of the reaction
State the colour of flame observed when lithium burns in oxygen
crimson red
State the colour of flame observed when sodium burns in oxygen
yellow-orange
State the colour of flame observed when potassium burns in oxygen
lilac
Describe the properties of noble gases. Discuss the trend in boiling point down the group.
n-m, gases, low boiling point, unreactive (full outer shell)
boiling point increases down the group, as the atoms get heavier
