Bridge Course Flashcards
Give two ways in which the plum pudding model differs from the current model
PROTONS and NEUTRONS in the nucleus
ELECTRONS in SHELLS
Describe the experimental evidence that shows the plum pudding model is incorrect
Most alpha particles passed straight through - most of atom is empty space
Some particles were deflected - there is a small positively charged nucleus
Give the relative masses and relative charges of each fundamental particle
Proton 1 +1
Neutron 1 0
Electron 1/1840 -1
What is the atomic number
Number of protons in the nucleus
What is the mass number
The number of protons and neutrons
How do you calculate the number of neutrons
mass no - atomic number
What is a cation and an anion
Cation - positive ion
Anion - negative ion
Why does the reactivity increase down Group 1 of the periodic table
As electron number increases down the group, atomic radius increases, meaning more shielding
Attraction between the nucleus and outer electron weakens
Meaning less energy is needed to remove the outer electron
What is an isotope
Atoms of the same element with the same number of protons but different number of neutrons
Do isotopes of the same element have the same or different CHEMICAL properties. why
Same chemical properties because they have the same number of electrons
Which physical properties of isotopes of the same element might be different
Mass, density, boiling points
What is the relative isotopic mass
The mass of an isotope compared with 1/12th of an atom of carbon-12
What is relative atomic mass
The weighted mean mass of an atom compared with 1/12th mass of an atom of carbon-12
Give all the diatomic substances
Hydrogen, nitrogen, fluorine, oxygen, iodine, chlorine and bromine
How do you calculate the empirical formula of a poly atomic molecule
- Make a column for each element
- Write the mass/percentage and divide by element’s Ar
- Divide all the answers by the smallest answer
- Find the simplest whole number ratio
- Write the empirical ratio
How do you calculate molecular formula from the empirical formula
- Find empirical formula
- Work out mass of empirical formula
- Divide Mr by empirical mass
- Multiply empirical formula by this answer
- Write molecular formula
How do you calculate the “water of crystallisation”?
1) Calculate the mass of the anhydrous salt: mass of crucible and residue - mass of crucible
2) Calculate the mass of water lost: mass of crucible and hydrated salt - mass of crucible and residue
3) Determine the ratio of anhydrous salt : water - write the mass of anhydrous salt and water and divide by their Mr ‘s - divide all answers by smallest answer
Do atoms of elements in group 4 tend to form ions? Why
No, they would have to either lose 4 electrons or gain 4 electrons.
Where in the periodic table are most elements able to lose different numbers of electrons.
- Central block of the periodic table, how many electrons an element can lose depends on what they are bonding to and what the environment is.
- These ions will have a roman numeral after the name e.g. nickel (II). The Roman numeral tells us the positive charge on the ion
How can you work out ionic formulae from the name of the compound
- Looking at the charge on both the cation and anion and using multiples so these positive and negative charges cancel out
Give the name and formula (with charge) of all the polyatomic ions
- Ammonium: NH4+
- Hydroxide: OH-
- Nitrate (V): NO3-
- Carbonate: CO3 2-
- Sulphate (VI): SO4 2-
The last three end in ate meaning it’s an anion with oxygens
How do you work out covalent formula
- Atoms that bond covalently don’t have charges: meaning we have to look at their names to give clues to formula
Mono: 1
Di: 2
Tri: 3
Tetra: 4
Penta: 5
Hexa: 6
Can you use halves to balance an equation?
- Yes, only if they are in front of a diatomic molecule
What order should you balance an equation in?
- Balance metals first
- Then non metals apart from H and O
- Then balance H and O
What is the practical method for determining the formula of a hydrated salt?
Apparatus:
- Crucible and lid
- Bunsen
- Heat proof mat
- Tripod
- Clay-pipe triangle
- Tongs
- Access to a top pan balance
Method:
- Weigh a crucible and its lid on a top pan balance. Record its mass.
- Using a spatula, add roughly 3 scoops of hydrated salt to the crucible and re weigh. Record the mass.
- Heat the crucible over a blue Bunsen flame for approximately 5 minutes. Remove the lid of the crucible at regular intervals to allow water to evaporate
- Let it cool on a heatproof mat before reweighing. Record the mass.
- Heat the crucible again for a further 5 minutes. Repeat step 4.
- Repeat steps 3 and 4 until a constant mass has been achieved.
