Chem Topic 1
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135 Terms
What did Dalton's model say about atoms?
Atoms were tiny, indivisible spheres.
Why did Dalton's model change?
The discovery of subatomic particles showed atoms contain smaller particles.
What is the structure of an atom?
A nucleus containing protons and neutrons, surrounded by electrons in shells.
What is the relative charge of a proton?
+1.
What is the relative mass of a proton?
1.
What is the relative charge of a neutron?
0.
What is the relative mass of a neutron?
1.
What is the relative charge of an electron?
−1.
What is the relative mass of an electron?
Very small, approximately 1/1836.
Why do atoms have no overall charge?
They contain equal numbers of protons and electrons.
How large is the nucleus compared with the atom?
The nucleus is extremely small compared with the overall atom.
Where is most of an atom's mass concentrated?
In the nucleus.
What is the mass number?
The total number of protons and neutrons in an atom.
What is the atomic number?
The number of protons in the nucleus.
What determines which element an atom is?
The number of protons in its nucleus.
What are isotopes?
Atoms of the same element with the same protons but different numbers of neutrons.
How do isotopes of an element differ?
They have different numbers of neutrons.
Why can relative atomic masses be non-whole numbers?
They are weighted averages of the masses of naturally occurring isotopes.
How do you calculate the number of neutrons?
Neutrons = mass number − atomic number.
How many electrons does a neutral atom have?
The same number as its protons.
How do you calculate relative atomic mass?
Multiply each isotope mass by its abundance, add them, then divide by total abundance.
Why did Mendeleev leave gaps in his periodic table?
He predicted undiscovered elements would fill the gaps.
What did Mendeleev use to arrange elements?
Their properties and the properties of their compounds.
How did Mendeleev predict undiscovered elements?
He used patterns in properties to predict their properties and masses.
Why was Mendeleev's arrangement not always increasing atomic mass?
Isotope abundances mean some elements have unusual relative atomic masses.
How are modern elements arranged?
In order of increasing atomic number.
What is a period?
A horizontal row in the periodic table.
What is a group?
A vertical column in the periodic table.
Why do elements in the same group have similar properties?
They have similar numbers of outer-shell electrons.
What does atomic number tell you?
The number of protons and an element's position in the periodic table.
Where are metals generally found in the periodic table?
On the left and centre.
Where are non-metals generally found?
On the right side of the periodic table.
Why are metals good at forming positive ions?
They tend to lose outer-shell electrons.
Why do non-metals tend to form negative ions?
They tend to gain electrons.
What is the electronic configuration of hydrogen?
1.
What is the electronic configuration of helium?
2.
What is the electronic configuration of lithium?
2.1.
What is the electronic configuration of carbon?
2.4.
What is the electronic configuration of oxygen?
2.6.
What is the electronic configuration of neon?
2.8.
What is the electronic configuration of sodium?
2.8.1.
What is the electronic configuration of magnesium?
2.8.2.
What is the electronic configuration of aluminium?
2.8.3.
What is the electronic configuration of silicon?
2.8.4.
What is the electronic configuration of chlorine?
2.8.7.
What is the electronic configuration of argon?
2.8.8.
How is electronic configuration related to periodic-table position?
The number of occupied shells gives the period; outer electrons relate to group.
What is an ionic bond?
The electrostatic attraction between oppositely charged ions.
How are ionic bonds formed?
By transfer of electrons between atoms.
What is a cation?
A positively charged ion.
What is an anion?
A negatively charged ion.
What is an ion?
An atom or group of atoms with a positive or negative charge.
How does a metal form a positive ion?
It loses electrons.
How does a non-metal form a negative ion?
It gains electrons.
What does Group 1 usually form?
1+ ions.
What does Group 2 usually form?
2+ ions.
What does Group 6 usually form?
2− ions.
What does Group 7 usually form?
1− ions.
How do you calculate electrons in a positive ion?
Subtract the ion's charge from the atomic number.
How do you calculate electrons in a negative ion?
Add the magnitude of the charge to the atomic number.
What does the ending -ide usually indicate?
A simple negative ion or binary compound.
What does the ending -ate usually indicate?
A compound containing a polyatomic ion with oxygen.
What is the formula of sodium chloride?
NaCl.
What is the formula of magnesium chloride?
MgCl₂.
What is the formula of aluminium oxide?
Al₂O₃.
What is the formula of calcium hydroxide?
Ca(OH)₂.
What is the formula of sodium nitrate?
NaNO₃.
What is the formula of calcium carbonate?
CaCO₃.
What is the formula of magnesium sulfate?
MgSO₄.
How do you work out an ionic compound formula?
Balance the charges so the overall compound is electrically neutral.
What is the structure of an ionic compound?
A giant lattice of regularly arranged positive and negative ions.
What holds an ionic lattice together?
Strong electrostatic attractions between oppositely charged ions.
Why do ionic compounds have high melting points?
Strong attractions between ions require lots of energy to overcome.
Do solid ionic compounds conduct electricity?
No, their ions cannot move freely.
Do molten ionic compounds conduct electricity?
Yes, their ions are free to move.
Do ionic compounds conduct electricity in aqueous solution?
Yes, their ions are free to move.
What is a covalent bond?
A shared pair of electrons between two atoms.
What does covalent bonding form?
Molecules or giant covalent structures.
What is the typical size of an atom?
About 1 × 10⁻¹⁰ m.
What is the typical size of a small molecule?
About 1 × 10⁻⁹ m.
What is the formula of hydrogen?
H₂.
What is the formula of hydrogen chloride?
HCl.
What is the formula of water?
H₂O.
What is the formula of methane?
CH₄.
What is the formula of oxygen?
O₂.
What is the formula of carbon dioxide?
CO₂.
Why do simple molecular substances have low melting points?
Weak intermolecular forces require little energy to overcome.
Do simple molecular substances usually conduct electricity?
No, they have no freely moving charged particles.
What are giant covalent substances?
Structures containing many atoms joined by strong covalent bonds.
Which two giant covalent forms of carbon are required?
Diamond and graphite.
What is the structure of diamond?
Each carbon bonds covalently to four other carbon atoms in a giant 3D structure.
Why is diamond very hard?
Strong covalent bonds form a rigid 3D structure.
Why is diamond used in cutting tools?
It is extremely hard.
What is the structure of graphite?
Carbon atoms form layers; each carbon bonds to three others.
Why can graphite conduct electricity?
It has delocalised electrons that can move through the layers.
Why is graphite used as a lubricant?
Its layers can slide over each other.
Why is graphite used for electrodes?
It conducts electricity and has a high melting point.
What are fullerenes?
Forms of carbon made from carbon atoms arranged in hollow structures.
What is C₆₀?
A fullerene containing 60 carbon atoms.
What is graphene?
A single layer of carbon atoms arranged in hexagons.