2.1.1 Atomic Structure and Isotopes and 2.1.2 Compounds, formulae and equations Flashcards
What was stated in Dalton’s atomic theory?
- Atoms are tiny particles made of elements
- Atoms cannot be divided
- All the atoms in an element are the same
- Atoms of one element are different to those of other elements
What did Thompson discover about electrons?
- They have a negative charge
- They can be deflected by magnet and electric fields
- They have a very small mass
Explain the plum pudding model
Atoms are made up of negative electrons moving around in a sea of positive charge
What were Rutherford’s proposals after the gold leaf experiment?
- Most of the mass and positive charge of the atom are in the nucleus
- Electrons orbit the nucleus
- Most of atom’s volume is the space between the nucleus and the electrons
- Overall positive and negative charges must balance
Explain the current model of the atom
- Protons and neutrons are found in the nucleus
- Electrons orbit in shells
- Nucleus is tiny compared to the total volume of atom
- Most of atom’s mass is in the nucleus
Most of the atom is empty space between the nucleus and the electrons.
What is the charge of a proton?
1+
What is the charge of an electron?
1-
What particle has the same mass as a proton?
Neutron
Which two particles make up most of an atom’s mass?
Protons and neutrons
Which letter is used to represent the atomic number of an atom?
z
What does the atomic number tell us about an element?
Atomic number = number of protons in an atom
Which letter represents the mass number?
a
How is mass number calculated?
Mass number = Number of protons + number of neutrons
How to calculate the number of neutrons?
Number of neutrons = mass number - atomic number
Define isotope
Atoms of the same element with a different number of neutrons
Why do different isotopes of the same element react in the same way?
- Neutrons have no impact on the chemical reactivity
- Reactions involve electrons, isotopes have the same number of electrons in the same arrangement
What are ions?
Charged particles that are formed when an atom loses or gains electrons
What is the charge of the ion when electrons are gained?
negative
What is the charge of the ion when electrons are loss?
positive
What is the unit used to measure atomic masses called?
Unified atomic mass
Define relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon 12
What are the units of relative atomic mass?
No units
Define relative isotopic mass
The mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon 12
The relative isotopic mass is the same as which number?
Mass number
Which two assumptions are made when calculating mass number?
- Contribution of the electron is neglected
2. Mass of both proton and neutron is taken as 1.0 u
How to calculate the relative molecular mass and the relative formula mass?
Both can be calculated by adding the relative atomic masses of each of the atom making up the molecule or the formula
What are the uses of mass spectrometry?
- Identify unknown compounds
- Find the relative abundance of each isotope of an element
- Determine structual infomation
How does a mass spectrometer work?
- The sample is made into positve ions
- They pass through the apparatus and are seperated according to mass to charge ratio
- A computer analyses the data and produces mass spectrum
How is the group number related to the number of electrons?
Group number = number of electrons in the outer shell
Does the group number indicate horizontal or vertical column in the periodic table?
Vertical column
Do metals usually gain or lose electrons?
Lose electrons
What are the 4 elements that don’t tend to form ions and why?
The elements are beryllium, boron, carbon and silicon
Requires a lot of energy to transfer outer shell electrons
What are molecular ions?
Covalently bonded atoms that lose or gain electrons
What is the charge of an ammonium ion?
+1
NH₄⁺
What is the charge of a hydroxide ion?
-1
OH⁻
What is the charge of a nitrate ion?
-1
NO₃⁻
What is the charge of a carbonate ion?
-2
CO₃²⁻
What is the charge of a sulfate ion?
-2
SO₄²⁻
What is an empirical formula?
Simplest whole number ratio of atoms of each element present in a compound
How to calculate empirical formula?
- Divide the amount of each element by its molar mass
- Divide the answers by the smallest value obtained
- If there is a decimal, divide it by a suitable number to make it into a whole number
