[C3] Atoms, elements and compounds Flashcards
Define an isotope
atoms of the same element which have the same proton number but a different nucleon number
Define nucleon number
(mass number) as the total number of protons and neutrons in the nucleus of an atom
Define proton number
(atomic number) as the number of protons in the nucleus of an atom
Define the term solvent
It is the substance in which the solute is dissolved
Define the term solute
a solid that is dissolved in a solvent
Define the term solution
The mixture formed when a solute dissolves in a solvent
Define the term concentration
the amount of a substance in a defined space.
Name the 3 elements in an atom
Central nucleus (containing protons, neutrons)
Shells of electrons
Define an element
A substance that cannot be further broken down by any chemical reaction.
(Each element has a unique number of protons in its atom)
Define mixture
A mixture is made from different substances that are not chemically joined.
Define compound
A compound is formed when two or more atoms join together chemically, with covalent or ionic bonds
Describe the difference between a mixture and a compound {2}
- Mixture is made from different substances but not chemically joined together. They can be separated by physical methods.
-Compound is made from different substances when they are chemically joined together
Describe 4 differences between metals and non-metals [4]
(7 are listed on the other side)
Metals- Shiny, high melting points, good conductors of electricity and heat, high density, malleable
Non-metals- Dull, low melting points, poor conductors of electricity and heat, low density, Brittle
Describe the lattice structure of ionic compounds
A regular arrangement of alternating positive
and negative ions,
ex. the sodium chloride structure
How do you identify physical changes from chemical changes?
Physical changes are to do with the state of matter. The substance will be a different shape or size at the end but no new substances are formed.
Chemical changes produce a new substance and either absorbs or releases energy during the reaction. Chemical reactions are on a nuclear level
Give 2 examples of physical changes [2]
boiling water, melting ice, breaking a bottle, crumbling paper.
Give 2 examples of chemical changes [2]
burning wood, dissolving salt in water, and digesting food.
State the different forms of carbon [2]
Diamond, graphite
Describe the giant covalent structure of diamond
Every carbon atom is bonded to 4 other carbon atoms with strong covalent bonds
Describe the giant covalent structure of graphite
Each carbon is bonded by 3 strong covalent bonds to make a giant structure consisting of layers of hexagons
State the relative mass and charge for
- protons [2]
-neutrons [2]
-electrons [2]
Protons- mass= 1 charge= +1
neutrons- mass=1 charge= 0
electrons- 1/12000 charge= -1
State 2 uses for radioactive isotopes
- Used in medicine (sterilise equipment or treat cancer tumours)
- Used in industry (to detect leaks in pipes)
Why do isotopes have the same chemical properties?
Because they have the same number of electrons in their outer shells
Describe the formation of an anion
(state which atoms become anions)
If an atom gains electrons, there are more electrons than protons so, negative ions are formed
(Non-metals gain electrons to become anions)
What is the name of a negatively charged ion?
Anion
What is the name of a positively charged ion?
Cation
Describe the formation of a cation
(State which atoms become cations)
If an atom loses electrons, there are more protons than electrons, so a positive ion is formed
(Metals lose electrons to become cations)
Describe a noble gas outer shell
It is full (this is called the noble gas electronic structure)
When atoms react they achieve this stable _______ by losing or gaining electrons to form ions.
A. Noble Gas electronic structure
What is noble gas electronic structure?
When the outer shell of the atom is full
How are the elements arranged in the periodic table?
In proton number order
What are the columns in the periodic table?
Groups- elements with similar properties are grouped together
What does the Group Number tell you?
How many electrons are in the outer shell
ex. Group 1- Li, Na, K, all have 1 electron in their outer shell
Which group contains elements with full outer shells?
Group 8 (VIII)
What are the rows called?
Periods
(in period 1 Shell 1 is being filled, in period 2 Shell 2 etc…)
What is an ionic bond and how is it formed? [2]
Formed by the transfer of electrons.
The oppositely charged ions are held together by a strong electrostatic attraction, this is called an ionic bond. It is a bond between metallic and non-metallic elements
Define an ionic bond
An ionic bond is the strong electrostatic attraction between oppositely charged ions.
Define a covalent bond
A single covalent bond is a shared pair of electrons between 2 atoms
State how covalent bonds are formed
When non-metal elements react, their atoms join together with covalent bonds (a pair of electrons is shared)
Describe the differences in
Volatility, solubility, electrical conductivity
between ionic and covalent compounds
Volatility:
Ionic- low volatility
Covalent- high volatility
Solubility:
ionic- often not soluble in water
Covalent- mostly insoluble in water
Electrical conductivity:
ionic- does not conduct electricity solid, conduct when molten
Covalent- does not conduct electricity
Which has stronger forces of attraction between atoms and why?
A. Ionic compounds because of the strong force between the opposite charges
State the difference in melting point and boiling point between ionic and covalent compounds (in terms of attractive forces)
Melting point:
Ionic- High melting point due to strong forces of attraction
Covalent- Low melting point due to weak forces of attraction
Boiling point:
Ionic- High boiling point due to strong forces of attraction
Covalent- Low boiling point due to weak forces of attraction
Explain why graphite can conduct electricity when diamond cant [2]
Diamond has no delocalised electrons
Graphite conducts electricity because the fourth electron of every carbon atom is unbonded and moves among the layers in a sea of delocalised electrons
State some 3 properties of diamond
- Hardest natural substance
- Has a very high melting point
- Does not conduct electricity
Why is graphite used as a lubricant?
Because the layers are not bonded together with covalent bonds just a weak force of attraction so the layers can slide over each other, making graphite a good lubricant
Describe a use for diamond
Cutting tools or drill bits
Describe 2 uses for graphite
a lubricant or a conductor
Describe the macromolecular structure of silicon (IV) oxide
Similar structure to a diamond except instead of carbon, there are alternating silicon and oxygen atoms. It also has similar properties to diamond e.g hard, and high melting point
Which of the following would be a physical changes?
a) Acid base neutralisation
b) Metal displacement
c) Boiling ethanol
d) Combustion of magnesium
C
Because:
- When ethanol boils it changes from liquid to gas
Which of the following statements best describes activation energy?
a) The minimum energy released when colliding particles react
b) The minimum energy required for particles to react
c) The maximum energy required for particles to react
d) The maximum energy released when colliding particles react
B
Non-metallic elements form simple molecules with _______ _______ between atoms.
covalent bonds
What does a period (row) tell you about all the elements in that period?
How many electrons in a shell
Why are the noble gases very unreactive?
They have a full outer shell = most stable configuration
How are ions formed?
Positive ions - when they lose an electron
negative ion - when they gain an electron
What types of elements are iconic bonds formed between?
Metal and non-metal
Describe the structure of an ionic compound
- Big lattice structure
- Held together by electrostatic attraction
- Alternating between positive and negative ions
Why do atoms form covalent bonds ?
To obtain a more stable structure (full outer shell)
Give an example of a compound that contains at least 1 covalent bond
H², Cl², H²O, CH⁴, NH³ & HCL
Compare the volatility of ionic and covalent compounds [3]
- Ionic compounds have low volatility
- Giant covalent compounds have low volatility
- compounds have high volatility
Compare the solubility of ionic and covalent compounds
Iconic - Generally soluble
Covalent - Insoluble in water
What are the uses of graphite and why
Electrode because they conduct electricity and have hight boiling points
Lubricant because it’s slippery
Describe the structure of graphite
In graphite, each carbon is covalently bonded to 3 other carbons, forming layers
of hexagonal rings, which have no covalent bonds between the layers.
Describe the formation of ionic bonds between elements from Groups 1 and 7
when ionic bonds are formed between group 1 and 7:
- group 1 atom loses one electron and forms a +1 ion
- group 7 atom gains the electron the group 1 atom lost and becomes a -1
ion
Describe the formation of ionic bonds between metallic and
non-metallic elements
Metal + Non-metal: electrons in the outer shell of the metal atom are transferred
- Metal atoms lose electrons to become positively charged ions
- Non-metal atoms gain electrons to become negatively charged ions
Why do isotopes have the same properties?
- they have the same number of electrons in their outer shell
- electrons in the outer
shell is responsible for chemical reactions
First shell can have up to
___ electrons
Second shell can have up to ___ electrons
Third shell can have up to ___ electrons
2
8
8
Which change to an atom occurs when it forms a positive ion?
A )It gains electrons.
B ) It gains protons.
C )It loses electrons.
D It loses protons.
C
“Electrons from each element are shared by both of the elements in a compound.”
Which compound matches this description?
A ) lead bromide
B ) sodium chloride
C ) water
D ) zinc oxide
C
Which statement about bonding is not correct?
A ) Carbon can form four single covalent bonds.
B) Chlorine atoms react to gain a noble gas electronic structure.
C) Covalent bonding involves losing and gaining electrons.
D) Hydrogen molecules have the formula H2.
C
Why are small covalent molecules liquids or gases at room temperature?
- When small molecules melt or boil, it’s the weak intermolecular forces that break.
- Since these intermolecular forces are weak and break easily, simple covalent molecules have very low melting and boiling points.
- Therefore, they exist as liquid and gases at room temperature.
Why do ionic compounds have a low electrical conductivity when not in a solution but a high electrical conductivity when dissolved in a solution?
- When not in a solution the ions are not free to move so cannot create a current.
- When they get dissolved in a solution, the ions can move around and so can create a current very easily.
