Chemistry Flashcards
What is an element?
An element is a pure substance that cannot be broken down or separated into anything simpler than it already is. Gold and carbon are examples of elements.
What are the two main types of elements and how do they differ?
Metals
- Are hard solids at room temperature
- Shiny
- Malleable (can be hammered or pressed out of shape)
- Ductile (can be drawn into a thin wire)
- Good conductors of heat and electricity
Non-Metals
- Are gases or brittle solids at room temperature
- Not shiny
- Not malleable
- Not ductile
- Not good conductors of heat and electricity
What are chemical symbols?
Each of the elements has a chemical symbol for its name of one or two letters. Examples:
H = hydrogen
C = carbon
Mg = magnesium
K = potassium
Na = sodium
What are the three most common elements in the Human Body?
- Oxygen
- Carbon
- Hydrogen
Proton
Electric charge: ______
Location in the atom: _______
Mass: ______
Electric charge: positive
Location in the atom: nucleus
Mass: 1
Neutron
Electric charge: ______
Location in the atom: _______
Mass: ______
Electric charge: Neutral
Location in the atom: Nucleus
Mass: 1
Electron
Electric charge: ______
Location in the atom: _______
Mass: ______
Electric charge: negative
Location in the atom: shells around the nucleus
Mass: ~0
What is an atom?
An atom is a particle of matter that uniquely defines a chemical element
What is a nucleus?
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom
What is a shell?
According to Bohr’s Atomic Model electrons revolve around the nucleus in a specific circular path known as an orbit or called a shell
What organizes the elements according to their physcial and chemical properties?
periodic table
The periodic table is divided into seven horizontal rows called ______ and 18 vertical columns called _____
The periodic table is divided into seven horizontal rows called families or groups and 18 vertical columns called periods
What type of elements appear on the left side of the periodic table?
Metals
Metals are ___ conductors of heat and electricity
Good
______ appear on the right side of the periodic table
Non-Metals
Non-metals are _____ conductors of heat and electricity
Poor
The _____ form a zigzag staircase arrangement on the periodic table.
Metaloids
Metaloid elements have properties similar to both ____ and ____
metals and non-metals
The _______ refers to the number of protons that an atom has in the nucleus
atomic number
The ______ is the weighted average of the masses of the atoms of an element
average atomic mass
The _____ is an electric charge that forms on an atom when it gains or loses electrons
ion charge
The ____ are inert or do not react with other elements
noble gases
The noble gases are on the ____ side of the periodic table
right-hand
The _____ elements are very reactive and are in second column in from the right-hand side of the periodic table
halogens
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element: Phosphorus
symbol: P
atomic number: 15
average atomic mass: 31
ion charge: 3-
number of protons: 15
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element: Magnesium
symbol: Mg
atomic number: 12
average atomic mass: 24
ion charge: 2+
number of protons: 12
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element: Potassium
symbol: K
atomic number: 19
average atomic mass: 39
ion charge: +
number of protons: 19
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element:
symbol:
atomic number:
average atomic mass:
ion charge:
number of protons:
name of element: Titanium
symbol: Ti
atomic number: 22
average atomic mass: 48
ion charge: 4+ and 3+
number of protons: 22
Name the families of elements – use the colour map
What is a chemical family?
Elements in a group or a vertical column have similar properties and so they are called a chemical family
What are properties of alkali metals?
In the far left column
Metallic elements that are strongly reactive, soft, and have low densities.
Examples: Potassium, Sodium
What are properties of alkaline earth metals?
Are in the second column from the left
metallic elements, that are reactive, fairly soft, and have fairly low densities.
Examples: Calcium and Magnesium
What are properties of halogens?
Second to the right column
non-metallic elements that are strongly reactive and are gases at room tempertature (except for bromine, which is a liquid)
What are properties of noble gases?
Far right column
non-metallic elements that are very unreactive and are colourless, odourless gases at room temperature
What is the periodic table?
The periodic table places each element on a chart based on it chemical and physical properties.
What can you see on the periodic table? What information is there for each element?
- name of the element
- chemical symbol of the element
- atomic number of the element
- average atomic mass of the element
- the ion charge (or charges) of the element
What is the atomic number of the element?
the number of protons in the nucleus of each one if its atoms
What is the average atomic mass of the element?
the weighted average of the masses of the atoms of the element
What is the ion charge of the element?
the electric charge of its atoms when they gain or lose electrons. If the atoms can gain or lose elctrons in more than one way, the will have a multiple ion charge
How do you find the number of protons?
it is equal to the atomic number
How do you find the number of neutrons?
take the atomic mass and (rounded up or down) and minus the atomic number (which is the number of protons)
How do you find the number of electrons?
in an atom the number of electrons is equal to the number of protons in an atom (the number of protons equals the atomic number)
Define an ion
is an atom where the number of electrons is different from the number of protons – it will have a positive or negative charge
if there are more protons then electrons, will have a positive charge
if there are more electrons then protons, will have a negative charge
An _____ (atom/ion) of an element has the same number of protons as electrons
atom
An ____ (atom/ion) has a different number of protons as electrons
ion
A positively charged ion has ____ (lost/gained) electrons
lost
A negatively charged ion has ____ (lost/gained) electrons
gained
What is a valence shell
a valence shell is the outermost occupied energy shell of an atom
What are valence electrons
valence electrons are the electrons in the outermost occupied energy shell of an atom
How many electrons are in the:
- first energy shell
- second energy shell
- third energy shell
- first energy shell – 2
- second energy shell – 8
- third energy shell – 8
Total number of electrons in first three shells: 18
Use your periodic table – answer the following for a neon atom –
atomic number:
number of protons:
number of electrons:
number of electron shells:
atomic number: 10
number of protons: 10
number of electrons: 10
number of electron shells: 2
Use your periodic table – answer the following for a sodium ion -
atomic number:
number of protons:
number of electrons:
number of electron shells:
atomic number: 11
number of protons: 11
number of electrons: 10
number of electron shells: 2
Use your periodic table – answer the following for a chlorine ion -
atomic number:
number of protons:
number of electrons:
number of electron shells:
atomic number: 17
number of protons: 17
number of electrons: 18
number of electron shells: 3
Use your periodic table – answer the following for a potassium atom -
atomic number:
number of protons:
number of electrons:
number of electron shells:
atomic number: 19
number of protons: 19
number of electrons: 19
number of electron shells: 4
What is a physical change?
During a physical change, a substance changes in form but not its chemical composition. No new substances are formed.
All changes of state (eg. water to solid, water to gas) are physical changes. Other physical changes including cutting, grinding and tearing substances.
Give two examples of a physical change.
- Ice melting is an example of a physical change. Some of the properties of liquid water are different from the properties of solid water. But the chemical composition of the water has not changed and no new substances have been produced.
- Dissolving salt in water is also a physical change. The individual salt ions and water molecules do not change when salt is dissolved in water.
What is a chemical change?
A chemical change causes of one of more new substances to be formed. Each new substance has properties and chemical compositions that are different from the original.
In a chemical change, new chemical bonds are formed while other chemical bonds are broken.
What is an example of a chemical change?
Burning paper is an example of a chemical change. The smoke that escapes and the grey-black solid that is left behind (ash) are new substances.
What are ‘reactants’ in a chemical change?
Reactants are the starting substances in a chemical change.
What are ‘products’ in a chemical change?
The products are the substances that result from the chemical change.
How can you tell if a change is a chemical change?
If you can make two or more of the following observations, then a chemical change probably has taken place:
Best things to look for:
- One or both reactants are used up.
- Gas bubbles form in a liquid.
OK things to look for:
- Heat is produced or absorbed.
- A solid forms in a liquid.
Not as good an indicator:
- There is a change in colour.
How is energy involved with physical and chemical changes?
All changes in matter involve changes in energy. Energy is either released or absorbed. The energy is often in the form of heat, but it may also be in the form of sound or light.
What does ‘exothermic’ mean?
Exothermic is the term used for the release of energy.
Water freezing, iron rusting and natural gas burning are examples of exothermic changes.
What does ‘endothermic’ mean?
Endothermic describes when energy is absorbed.
Cooking an egg, baking bread and melting ice are examples of endothermic changes.
How do compounds form?
A compound is a pure substance that is made up of two or more types of atoms that are joined together due to a chemical change.
Atoms are held together in compounds by chemical bonds. These chemical bonds are created by attractive forces between atoms.
Chemical bonds are formed when atoms gain or lose electrons, or when they share electrons.
Unlike a compound, an element is a pure substance that is made up of one type of atom.
What are some examples of compounds?
- Water
- Sugar
- Table salt
What happens to an atom when it loses an electron?
It becomes positively charged.
What happens to an atom when it gains an electron?
It becomes negatively charged.
What are ionic compounds?
If atoms gain electrons from other atoms or lose electrons to other atoms, they form ionic compounds. Ionic compounds usually form between metals and non-metals.
Why? The atoms in metal tend to lose electrons. So metals have a positive charge when they form ions. The atoms in non-metals tend to gain electrons. So non-metals have a negative charge when they form ions.
How do ionic compounds form?
When atoms of a metal come near atoms of a non-metal, they may join together to form an ionic compound. Electrons from the metal atoms are transferred to the non-metal atoms to create oppositely charged ions that attract each other.
For example, when a sodium atom (metal) comes near a chlorine atom (non-metal), the sodium atom loses an electronc to form a positive ion, and the chlorine atom gains an electron to form a negative ion. The two oppositely-charged ions are attracted to each other.
How to covalent compounds form?
Sometimes atoms share electrons instead of losing and gaining them. If the atoms share electrons, they form covalent compounds.
Covalent compounds form when non-metal atoms bond together by sharing their electrons. Since the electrons are shared, the particles that make up covalent compounds are neutral. They do not have a charge.
A neutral particle that is made up of atoms that are joined together by covalent bonds is called a molecule.
What is a molecule and provide an example
A molecule is a neutral particle that is made up of atoms that are joined together by covalent bonds.
Water is a covalent compound. Its molecules are made of hydrogen and oxygen.
What is a polyatomic ion?
Some ions contain more than one atom.
In these many-atom ions, the atoms are held together with covalent bonds. But the many-atom unit has a charge, so it is considered an ion.
An ion that is made up of two more atoms that are held together with covalent bonds is called a polyatomic ion.
For example, the nitrate ion contains nitrogen and oxygen.
Can two metals form a compound
No, two metals can not bond together
What is a chemical formula
A chemical formula shows the number of atoms of each elemet present in the compound – ie. H2O – 2 hydrogens atoms and one oxygen
Finishing filling in the following:
Sugar – C12H22O11
___ parts carbon ___ parts hydrogen ___ parts oxygen
Total number of atoms = _____
12 parts carbon, 22 parts hydrogen, 11 parts oxygen
Total number of atoms = 45
Alcohol
2 parts carbon, 6 parts hydrogen, one part oxygen
What is the formula? ____
Total number of atoms: ____
C2H6O
Total number of atoms: 9
Sulphuric Acid
H2SO4
___ parts hydrogn, ___ parts sulphur, ___ parts oxygen
Total number of atoms: _____
2 parts hydrogn, 1 parts sulphur, 4 parts oxygen
Total number of atoms: 7
A pure substance that is made up of one type of atom is called a(n)…
element
A pure substance that is made up of two or more types of atoms that are joined together due to a chemical charge is called a(n)…
compound
Atoms in a molecule and ions in a ionic lattice are held together by …
chemical bonds
Chemical bonds are formed when atoms gain or lose ____ or when they share _____
electron
Metals and non-metals may form ______
ionic compounds
Ionic compound is a ______
compound made up of oppositely charged ions (one is negative and one is positive)
An ionic bond is _____
a strong atraction that forms between oppositely charged ions
What do elements in the same group have in common (vertical, up-and-down column)?
they have the same number of valence electrons (valence electrons are the electrons occupying the outermost shell)
What do elements in the same period (horizontal, left to right row) have in common?
They have the same number of energy shells
Which elements have a full valence shell?
Noble gases – this is what makes them stable
What is a periodic trend
These refer to a pattern in the properties of elements on the periodic table. These trends help us to predict the properties of an element
What is the periodic trend (or pattern) relating to atomic size when you move down a groups (up and down column)?
The atomic size increases as you move down a group – because it has more occupied energy shells and its valence electroncs are farther away from the nucleus
What is the periodic trend (or pattern) relating to atomic size as you move from left to right across a period?
Atomic size decreases as you move from left to right across a period because the postive protons pull on the negative electrons bringing them closer to the nucleus
What is the maximum number of electrons that can be found in the:
- first energy shell
- second energy shell
- third energy shell
- first energy shell – 2
- second energy shell – 8
- third energy shell – 8
Why do atoms become ions?
Because atoms want full valence shells
Do metals become more or less reactive as you move down a group (column)?
increases – becomes more reactive – as you move down a group the atoms get bigger, so the valence electrons are farther from the nucleus and there is less pull on them – more likely to bond with another element
What to do with elements with multiple ion charges? –> multivalent metals?
A) If you are given the charge (+1, +2, +3, …) use it directly in the cross rule
B) if you are given the chemical name, the ion charge that you use will be a ROMAN NUMERAL in that name (I, II, III, IV, V ….)
Chemical Formulas – Why do some formulas have NO NUMBERS in the (NaCl), while other DO have number (Fe2O3)?
- atoms will ‘swap or share’ electrons in order to have a full/stable outer shells (valence shells)
- the ION CHARGE tells us how many electrons a particular atom wants to gain or lose to become stable
- the CROSS RULE (** for ionice compounds – what are these again?) is the tool/shortcut that helps you determine IF atoms will react, and how many atoms will need to involved
Chemical Formulas – How do you deal with POLYATOMIC IONS?
Use the table of polyatomic ions to look up the ION CHARGE and then use the CROSS RULE
Chemical Formulas – Covalent compounds (non-metals with non-metals)
- NO cross rule
- Get the formula by directly translating hte name (and using/knowing the prefixes)
1 = mono
2 = di
3 = tri
4 = tetra
5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
Write the formula for this covalent compound – Dinitrogen Tetraoxide
N2O4
Write the formual for this covalent compound – Carbon dioxide
CO2
Write the formula for this covalent compound – triphosphorus pentasulphide
P3S5
