Topic 1 - Key Concepts in Chemistry✅

Ok btw this hasn't got a flashcard for every single spec point, just the more hard to remember stuff. I haven't rly done a flashcard for any of the 'recall' stuff about atoms. And none of the calculations etc

How did Mendeleev arrange elements of the periodic table

• Ordered his table in order of atomic mass

• Left gaps for elements that weren't yet discovered

How did Mendeleev use his table to predict the existence and properties of some elements

• Mendeleev realised elements with similar properties belonged in the same groups in the periodic table so was able to leave gaps and place the discovered elements where they fit best

• Elements with properties predicted by Mendeleev were later discovered and filled the gaps

What part of his table did Mendeleev get wrong

• He thought he arranged the elements in order of increasing relative atomic mass

• But this was not always true due to the relative abundance of isotopes of some pairs of elements

How are elements in the periodic table arranged now

• In order of increasing atom number, in rows called periods

• Elements with similar properties are placed in the same vertical columns, called groups

How has Dalton's model of an atom changed over time

• Dalton's atom theory stated that atoms could not be broken down into smaller parts

• However research in the 1890s made it clear that subatomic particles, aka electrons, do exist

Describe the structure of an atom

• Nucleus containing protons and electrons

• Surrounded by electrons in shells

Charge and mass of proton

Charge +1

Mass 1

Charge and mass of neutron

Charge 0

Mass 1

Charge and mass of electron

Charge -1

Mass negligible

Why do atoms contain equal numbers of protons and electrons

• To obtain a neutral charge

• Since protons and electrons have equal and opposite charges, this means that atoms have no overall electrical charge.

What is mass number of an atom

The mass number of an atom is its total number of protons and neutrons.

What is an isotope

• Different atoms of the same element

• Same number of protons but different number of neutrons

What is an ionic bond

The electrostatic force of attraction acting between oppositely charged ions

How are ionic bonds formed between a metal and a nonmetal

• Electrons in the outer shell of the metal atom are transferred

• Metal atoms lose electrons to become cations

• Nonmetal atoms gain electrons to become anions

What is an anion / cation

Anion = atom with a negative charge Cation = atom with a positive charge

What does the -ide ending mean

It means the compound contains at least 2 elements, one of which is a nonmetal anion

What does the -ate ending mean

It means the compound contains at least 3 elements, one of which is oxygen

What is the structure of an ionic compound

• Lattice structure

• Regular arrangement ions

• Held together by strong electrostatic forces between oppositely charged ions

What is a covalent bond

• Covalent bond is the electrostatic forces of attraction

• between the nuclei of two atoms

• and the shared pair of electrons

What is the result of a covalent bond

Molecules

Properties of ionic compounds

• High MP and BP because lots of energy is required to break the many strong bonds

• When molten or aqueous they can conduct electricity as ions are free to move

• They do not conduct electricity as solids

Properties of simple molecular compounds

• Low MP and BP due to weak intermolecular forces

• Do not conduct electricity because they don't have electric charges

Properties of giant covalent structures

• Very high MP due to strong covalent bonds between atoms

• Some can conduct elec

Properties of metallic structure

Metals have giant structures of atoms with strong metallic bonding Most metals have high MP and BP Can conduct heat and elec because of delocalised electrons Layers of atoms can slide over each other, so they are malleable

What are graphite and diamond

• Different forms of carbon

• Giant covalent substances

Structure and properties of diamond

• Each carbon is joined to 4 other carbons by covalent bonds

• Hard

• High MP

• Does not conduct electricity

Structure and properties of graphite

• Each carbon is covalently bonded to 3 others

• This forms layers that can slide over each other

• The layers have weak intermolecular forces

• Graphite is soft and slippery

• One electron from each carbon is delocalised, meaning it can conduct electricity

What are graphite's uses and why

Electrodes Can conduct electricity   Lubricants Weak intermolecular forces No covalent bonds between layers Therefore soft and slippery

What is diamond's use and why

Cutting tools

• Very hard

• Due to rigid structure

Properties of buckminsterfullerene

• There are weak intermolecular forces between molecules

• Therefore slippery + low melting point

Properties of graphene

• There are strong covalent bonds between the carbon atoms

• This means graphene has a very high melting point and is very strong

• It can conduct electricity well due to delocalised electrons

What are polymers

Polymers consist of large molecules containing chains of carbon atoms

Properties of metals and why

Malleable

• Layers of atoms can slide over each other

Electrical conductors

• Delocalised electrons can move

Limitations of dot and cross diagrams

Do not show how ions are arranged in space

Limitations of ball and stick models

Do not show the bonds between ions

Limitations of 3D models

• Not to scale

• Gives no information about forces of attraction between ions, or movement of electrons to form ions

Limitations of 2D diagrams

Does not show where ions are located on the other layers

Describe most metals

• Shiny solids

• High melting points

• High density

• Good conductors of electricity

Describe most non-metals

• Low boiling points

• Poor conductors of electricity

What is the law of conservation of mass

• No atoms are lost or made during a chemical reaction

• Mass of products = mass of reactants

How does law of conservation of mass apply to precipitate reactions

• Precipitate that forms is insoluble and solid, as all the reactants and products remain in the sealed reaction container

• Easy to see that the total mass is unchanged

How does the law of conservation of mass apply when the reaction is done in an open flask

• In an open flask gas may be taken in or given out

• Meaning the mass will change from what it was at the start, as some mass is lost when the gas is given off