2.1.1 Atomic structure and Isotopes Flashcards
What was stated in Dalton’s atomic theory? (4)
- 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? (3)
- They have a negative charge
- They can be deflected by magnett and electric field
- They have 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 proposal after the gold leaf experiment? (4)
- 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 a proton?
1+
What is the charge of an electron?
1-
Which particle has the same mass as proton?
Neutron
Which two particles make up most of the 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 = no. protons
Which letter represents the mass number?
A
How is the mass number calculated?
Mass number = no. protons + no. neutrons
How to calculate the number of neutrons?
Number of neutrons = mass number - atomic number
Define isotope
Atoms of the same element with different number of neutrons but the same number of electrons and protons
They therefore have different masses
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 is formed when an atom loses or gains electrons
What is the charge of the ion when electrons are gained?
Negative
What is the unit used to measure atomic masses called?
Unified atomic mass unit, u
Define relative atomic mass
The weighted mean mass of an atom of na element compared with one twelfth of the mass of an atom of carbon 12
What is the unit of relative atomic mass?
No units
Define relative isotopic mass
The mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon 12
The relative isotopic mass is same as which number?
Mass number
What two assumptions are made when calculating mass number?
Contribution of the electron is neglected
Mass of both proton and neutron is taken as 1.0u
How to calculate the relative molecular mass and 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 relative abundance of each isotope of an element
Determine structural information
How does a mass spectrometer work?
The same is made into positive ions
They pass through the apparatus and are separated 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
Which 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 ammounium 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
CO3 2-
What is the charge of a sulfate ion?
-2
SO4 2-
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 by a suitable number to make it into a whole number
