Properties and Structure of Matter

Define a ‘pure substance’

A substance which is made up of a single chemical species (element, compound, molecule). It cannot be separated any smaller without breaking chemical bonds

Are pure substances homogeneous or heterogeneous?

Always homogeneous

Define a ‘mixture’

When two or more pure substances are mixed together (not chemically bonded)

Are mixtures homogeneous or heterogeneous?

They can be either

What are separating techniques used for?

To separate a mixture into its pure substances

What are all the different separation techniques?

* distillation (solution or mixture of liquids)
* fractional distillation (similar boiling point)
* sieve
* filtration (size)
* vaporisation (solid dissolved in liquid)
* immiscible liquids (not homogeneous)
* magnets
* solubility
* density
* boiling point

What is a binary ionic compound?

An ionic compound with 1 type of cation and 1 type of anion

What are the IUPAC naming conventions for binary ionic compounds?

The cation is named first and then the anion. The cation stays as the same name as the element, the anion is changed at the end to ‘-ide’ (e.g. sodium chloride)

What are simple inorganic covalent compounds?

Covalent, binary compounds which are not carbon based

What are the Greek prefixes, up to 10?

Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

What are organic covalent compounds?

Compounds with carbon-carbon or carbon-hydrogen covalent bonds

What are the IUPAC naming conventions for binary covalent compounds?

Least electronegative first, the second element has the suffix ‘-ide’ added, the number of each atom is represented by a Greek prefix

What is the symbol and charge for hydroxide?

OH -1

What is the symbol and charge for carbonate?

CO3 -2

What is the symbol and charge for nitrate?

NO3 -1

What is the symbol and charge for ammonium?

NH4 +1

What is the symbol and charge for phosphate?

PO4 -3

What is the symbol and charge for sulfate?

SO4 -2

What is periodicity?

The relationship between elements’ physical/chemical characteristics and their position on the periodic table

List some physical properties

Brittleness, malleability, shinyness, hardness, boiling point, melting point, heat capacity, heat conductivity, viscosity, density, ductility, colour, transparency, reflectivity, refractivity, absorption, lustre, electrical conductivity, resistance, electrical charge

Is brittleness a physical or chemical property?

Physical

Is malleability a physical or chemical property?

Physical

Is shinyness a physical or chemical property?

Physical

Is hardness a physical or chemical property?

Physical

Is boiling point a physical or chemical property?

Physical

Is melting point a physical or chemical property?

Physical

Is heat capacity a physical or chemical property?

Physical

Is heat conductivity a physical or chemical property?

Physical

Is viscosity a physical or chemical property?

Physical

Is density a physical or chemical property?

Physical

Is ductility a physical or chemical property?

Physical

Is colour a physical or chemical property?

Physical

Is transparency a physical or chemical property?

Physical

Is reflectivity a physical or chemical property?

Physical

Is refractivity a physical or chemical property?

Physical

Is absorption a physical or chemical property?

Physical

Is lustre a physical or chemical property?

Physical

Is electrical conductivity a physical or chemical property?

Physical

Is resistance a physical or chemical property?

Physical

Is electrical charge a physical or chemical property?

Physical

List some chemical properties

Acidity, basicity, combustibility, ability to oxidise or reduce

Is acidity a physical or chemical property?

Chemical

Is basicity a physical or chemical property?

Chemical

Is combustibility a physical or chemical property?

Chemical

Is the ability to oxidise or reduce a physical or chemical property?

Chemical

What is the atomic number?

The number of protons in an element

What is the mass number?

The sum of protons and neutrons (the nucleus) in an element

What does the number of neutrons in an element define it by

Its isotope

What is the structure of an atom?

The protons (positive charge) and neutrons (neutral charge) make up the dense nucleus and electrons (negative charge) orbit the nucleus. The protons and electrons are the same number in order for the atom to be neutral

How is the periodic table arranged?

Elements are arranged in increasing order of atomic number

What is the word for the horizontal rows in the periodic table?

Periods/series

What is the word for the vertical columns in the periodic table?

Groups

What are the 3 broad classes of elements on the periodic table?

Metals, non-metals, and metalloids

What are isotopes defined by?

How many neutrons they have

What are isotopes?

The same element with varying number of neutrons

What is an example of an isotope?

Carbon-14

What is a radioisotope?

An isotope which emits radiation to change into a different isotope due to its instability (it undergoes radioactive decay)

What is radioactive decay?

The emission of energy via ionising radiation

Is radioactive decay spontaneous or not?

It is spontaneous

What is a nuclear reaction?

A nucleus gaining stability by changing

What occurs to stability of an element as the atomic number increases?

Stability decreases as atomic number increases

which element is the point at which all following elements on the periodic table are unstable and why is this?

Bismuth (83) due to the nuclei all being too large

What is a mass spectrometer used for?

It is used to find the relative proportions of isotopes

How do you calculate relative atomic mass from a mass spectrometer?

1. convert each % to decimals
2. multiply each decimal by the mass number of the isotope
3. Add the values

e.g. Mr(Cl) = (0.7578 x 35) + (0.2422 x 37) = 35.48

What does Mr stand for?

Relative atomic mass

What are the only elements that are found in nature as individual atoms?

Noble gasses

What does nature want the energy configuration of atoms to be at?

At the lowest energy configuration possible as it is the most stable configuration

How do unstable atoms gain a noble gas configuration?

By bonding to other unstable atoms

What are anions?

Negatively charged ions (gained electrons)

What are cations?

Positively charged ions (lost electrons)

What do anions and cations create when they bind together?

Ionic compounds which have an overall neutral charge

Are there molecules of ionic compounds?

No, they are large arrays/networks of positive and negative ions

What is the empirical formula?

The simplest ratio of cations to anions within an ionic compound

What is the formula for ionic compounds?

AxBy

In the ionic compound formula AxBy, what do X and y represent?

The smallest possible values of the

What is the crossing over method to find the formula of ionic compounds?

Al3+ O2-

/

/

/

Al2 O3

What elements generally form ionic compounds?

Elements that are only 1 or 2 elements away from a noble gas (groups 6 or 7) with elements from groups 1 and 2

What kind of compounds can elements from groups 1 and 2 form?

They can ONLY form ionic compounds

What kind of compounds can elements from groups 6 and 7 form?

Ionic or covalent compounds

How do covalent bonds achieve a noble gas configuration?

By sharing electrons between elements

Which elements can form covalent bonds?

Only elements from the right hand side of the periodic table

How can covalent bonds be represented/denoted?

By a dash (Cl-Cl) or by a Lewis dot diagram

What does the valency of an element indicate about bonds in a covalent compound?

The valency of an element is the number of bonds it forms in a covalent bond

What is electronegativity?

The measure of electron attracting power of an element

When will elements form an ionic bond (regarding to electronegativity)?

When one element has a stronger electronegativity of >1.5

When will elements form a covalent bond (regarding to electronegativity)?

When the elements have a similar electronegativity (

When are covalent bonds polar?

When one atom has a greater electronegativity than the other

What is the order of electronegativity among the elements?

F > O > N = Cl > Br > C = S = I > P = H > Si

Are the following covalent molecules polar or not?: H-O, H-N, C-O, C-Cl

Polar

Are the following covalent molecules polar or not?: N-Cl, C-S, P-H

Non-polar

What symbol denotes electronegativity/charge of a molecule?

𝛿+ and 𝛿–

What is a ‘net dipole’?

When a polar molecule has an overall negative end and an overall positive end

Is a polyatomic molecule always polar if it has polar bonds within it?

No, within a polyatomic molecule, dipoles can cancel each other out and make the overall molecule non-polar even if it has polar bonds within it

What is polarity of a polyatomic molecule determined by?

The shape of the molecule and it must have at least one polar bond

What does VSEPR theory stand for?

Valence shell electron pair repulsion theory

What is VSEPR theory?

Valence electrons arrange themselves on the outer shell so that they are as far away from each other as is possible (this determines the shape of the molecule)

If a molecule has a total number of 2 electron pairs, 2 bonding pairs, and the arrangement of the electron pairs is linear, what shape will the molecule take?

Linear

If a molecule has a total number of 3 electron pairs, 3 bonding pairs, and the arrangement of the electron pairs is trigonal planar, what shape will the molecule take?

Trigonal

If a molecule has a total number of 4 electron pairs, 4 bonding pairs, and the arrangement of the electron pairs is tetrahedral, what shape will the molecule take?

Tetrahedral

If a molecule has a total number of 4 electron pairs, 3 bonding pairs, and the arrangement of the electron pairs is tetrahedral, what shape will the molecule take?

Trigonal pyramidal