CHO3001 Flashcards
What is an atom
-building block of all chemistry
-barely visible under most powerful microscope
-all elements are made up of atoms
Atomic theory
-all atoms are made up of smaller particles : protons, neutrons, electrons
-positive protons are strongly held together in the nucleus
-neutral neutrons are found in the nucleus to prevent protons from repelling
-negative electrons are much lighter than protons and neutrons
-electrons take up most space around nucleus due to repulsion between charges
-number of protons determine the type of element
-neutral atom has equal number of protons and electrons
Mass number
Total number of protons and neutrons in the nucleus of an atom
-symbol top left
-always refers to an isotope snd never directly to an element
Isotope
An atom of the same element that has a different number of neutrons
Atomic number
-number of protons
-written on bottom left
-only refer to one element
-if number of protons change then the element changes
How to calculate number of protons, neutrons and electrons
Protons = atomic number
Neutrons = atomic number (for neutral atom)
Neutrons = mass number - atomic number
Molar mass definition
The mass of one mole of substance in grams
Where are electrons found
In energy levels
How many electrons in different energy levels
First level, up to 2
Second level, up to 8
Third level, up to 18
What is electron configuration
Arrangement of electrons in energy levels
Where are valence electrons found
Outermost energy level
Groups and valence electrons
G1, 1
G2, 2
G13, 3
G14, 4
G15, 5
G16, 6
G17, 7
G18, 8 except for helium that has only 2
What does the atomic number of an atom tell us
The amount of electrons
When are atoms more stable
When they have full valence shells (outermost energy levels)
How can atoms obtain full outer energy levels
By bonding with each other which causes them to lose energy
What are the three types of bonding
Covalent
Ionic
Metallic
What is covalent bobding
-sharing of electrons between non-metal atoms
-atoms held together by electrostatic forces between shared electrons and nuclei of the atoms
What is ionic bonding
-transfer of electrons from a metal to a non-metal atom to form cations and anions
-held together by electrostatic attractive forces
What is metallic bonding
-attraction between delocalised valence electrons and the positive core of metal atoms
Molecules
A discrete group of atoms bonded together, which retains the chemical and physical properties of that substance.
Are noble gases reactive
Group 18, noble gases are very unreactive due to their full valence shell they are stable.
Bonding theory is based on the idea that :
-atoms will share, gain or lose electrons to acquire the electron arrangement of a noble gas.
For most atoms it means acquiring 8 electrons in highest energy level.
Hydrogen, Lithium and Beryllium become stable with just two electrons in their valence shell.
Aroms can share gain or lose electrons by forming chemical bonds.
Valency
A property of atoms or groups, equal to the number of atoms of hydrogen that the atom or group could combine or displace in forming compounds.
What is the valency of an element
The combining power of the element, and can be worked out from the formula of a compound or from the periodic table.
How is it shown that an element has variable valencies.
The valency is written as a roman numeral in brackets after the element name.
Polyatomic ion
Charged species composed of two or more covalently bonded atoms
Formula unit
The smallest repeating unit of a substance or the empirical formula of an ionic or covalent network solid compound.
Links
https://quizlet.com/_354m55. Cations
https://quizlet.com/_354php. Anions
https://quizlet.com/_35s0y3. Common valencies of elements and polyatomic ions
Rules for naming ionic compounds
- name of metal or ammonium group is written first : sodium chloride, ammonium nitrate
-if metal has more than one valency, the appropriate valency is indicated by a Roman numeral in brackets after the metal : Fe(OH)3 iron(iii) hydroxide or Fe(OH)2 iron(ii) hydroxide
-name of the non metal part of the compound is written second : NaCl sodium chloride
-if this is an element rather than a group, the ending of the name is -ide.
-non metal groups containing oxygen end in -ate or -ite.
Prefixes
- Mono
- Di
- Tri
- Tetra
- Pent
- Hex
- Hept
- Oct
Simple anions end in -ide (prefix derived from name of the element)
Cl– = chloride (chlorine + ide)
O2– = oxide (oxygen + ide)
S2– = sulfide (sulfur + ide)
Some polyatomic anions end in -ide (prefix not derived from name of element
OH– = hydroxide (? + ide)
CN– = cyanide (? + ide)
Anions ending in -ate and -ite
-ate always have more oxygen than -ite
SO4 sulfate SO3 sulfite
NO3 nitrate NO2 nitrtite
Prefix per is used if more oxygen atoms are present than usual or if the element has a higher oxidation state
-always end in ate
ClO3 chlorate ClO4 perchlorate
MnO4^-2 manganate MnO4^- permanganate
Prefix hypo is used if fewer oxygen atoms are present than usual, group name will always end in ite
ClO2^- chlorite ClO^- hypochlorite
When oxygen is replaced with sulfur prefix thio is used
SO4^-2 sulfate S2O3^-2 thiosulfate
OCN^- cyanate SCN^- thiocyanate
Acid
Substance that neutralises a base. Substance that releases H+ ions in solution
When anions joins H+ to form acid then ide or ate becomes ic acid and ite becomes ous acid
HNO3 nitric acid HNO2 nitrous acid
H2SO4 sulfiric acid H2SO3 sulfurous acid
HCl hydrochloric acid
Give anions for
Tartaric acid
Citric acid
Ethanoic acid
Tartrate
Citrate
Ethanoate
Two levels to Describe chemical reactions
Macroscopic level
Submicroscopic level
Give examples of descriptions at a macroscopic level
Word equations
Observations such as what can be seen, heard and felt.
Give examples of descriptions at a submicroscopic level
Explanations using models such as atomic model, bonding models, symbol equations and particles.
What is a symbol equation
It gives the symbol or formula of each substance and the state of each substance in a reaction
It shows what happens to the individual atoms of each element and/or compound and the numbers in which they combine.
What can be assumed about what happens to atoms
It can be assumed that what happens to a few atoms will happen to a large number of atoms, an in the same proportions of atoms.
What are spectator ions
Unreacting particles
What is a word equation
It describes a chemical equation by stating what chemicals reacted and what products were formed.
What should be included in an observation
What is seen, heard, smelled and how the substances are different at the end from what it was at the start.
All soluble
Nitrates (NO3)
Group 1 (Na, K)
Ammonium (NH4)
Chlorides (Cl)
Bromides (Br)
Iodides (I) Except Hg(i), Ag, and Pb salts
Sulfates (SO4) Except BaSO4, CaSO4, PbSO4
All insoluble
Oxides (O^2-) except group 1 and ammonium salts
Sulfides (S^2-) except group 1 and 2 and ammonium salts
Hydroxides (OH) except group 1 and ammonium salts
Carbonates (CO3)
https://quizlet.com/_3y4f2e
Required for word equation
-name reactants
-name products
-states can be included
Requirements for symbol equation
-give formulae for reactants
-give formulae for products
-states can be included
-give ratio in which the reactants react
-give ratio in which products are formed
Steps tor balancing equations
- Check if all formulae are correct, if so don’t change anything.
- Count nr of atoms of each element on either side of the equation
- Look at elements where nrs don’t match
- Balance equation by putting a number in front of the formula
- Remember number in front affects every element of formula
- Keep numbers as low as possible
- Balance single elements last
What is RAM
-Relative atomic mass
-doesn’t have any units
-atoms are compared to carbon-12 which has ram of 12.00.
What is RFM
-Relative formula mass
-sum of ram values of all atoms shown in formula of compound
-molecular compounds have relative molecular masses
What is a mole
-the amount of a substance containing the Avogadro number of particles where:
•amount is a quantity used for measuring substances
•particles can be atoms, molecules or formula units
A mole of these elements contain Na atoms :
-all metals
-group 18 noble gases
-carbon, phosphorus, sulfur
What should be specified when using the term ‘mole’
Whether you are referring to atoms of the element or the molecule for elements which can exist as diatomic molecules. (H2, N2, O2, Cl2)
A mole of a momecular compound contains …?
NA molecules
Include all compounds which are liquids and gases, and some solids
A mole of a metal compound contains…?
NA formula units of the compound
Particles : atoms
-all metals, lithium, magnesium, iron, copper
-noble gases, group 18, He, Ne, Ar
-carbon, sulfur, phosphorus
1 mole of copper contains NA copper atoms or 6.02 × 10^23 atoms.
½ mole of copper contains ½NA copper atoms or 3.01 × 10^23 atoms.
3 moles of copper contain 3NA copper atoms or 1.81 × 10^24 atoms.
Particles : diatomic molecules
This includes hydrogen (H2), nitrogen (N2), oxygen (O2), fluorine (F2), chlorine (Cl2), bromine (Br2) and iodine (I2).
All elements that are gases apart from group 18. One mole of an element that consists of diatomic molecules will contain NA number of particles.
Specify
1.a mole of oxygen atoms, or
2.a mole of oxygen molecules, or
3.give the formula as well as the name, so: a mole of oxygen, O, or a mole of oxygen, O2.
If diatomic molecule is a gas it implies the molecule.
Particles : compounds
Either molecular or ionic
Molecular compound
A molecular compound is usually a group of non-metal atoms from two or more different elements that are covalently bonded together.
Usually gases or liquids, but some solids like sugar
H2O & CO2
A mole of these compounds is the amount containing the Avogadro number of molecules
Ionic compounds include
metal compounds such as metal oxides and hydroxides (for example, MgO, Ca(OH)2, Fe2O3) and also salts (for example, CuSO4, NaCl, PbCO3).
Ionic compound
One mole of an ionic compound contains the Avogadro number of its ‘formula unit’.
Not made up of molecules
1 mole of iron(III) oxide, Fe2O3, contains NA Fe2O3 units made up from 2NA iron ions and 3NA oxide ions.
