Module 2 Flashcards
What was stated in daltons atomic theory?
- atoms are tiny particles made of elements
- atoms cannot be divided
- all the atoms in a 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 field
- They have very small mass
Explain the plumpudding 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?
- Most of the mass and positive charge of the atom are in the nucleus
- Elections 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 volume the total volume of atoms
- Most of atom’s mass is in the nucleus
- Most of 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-
Which particle has the same mass as protons?
Neutron
Which two particles make up most of an atoms mass?
Protons and neutrons
Which letter is used to represent the atomic number of an atom?
Z
What does the atomic number tell 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 different number of neutrons
Why does different isotopes of the same element react in the same way?
- Neutrons have no impact, on the chemical reactivity
- Reactions involve elections, 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 change of the ion when elections are gained?
Negative
What is the unit used to measure atomic masses called?
Unified atomic mass unit, u
Define relative atomic mass
The weighed mean mass of an atom of an element compared with 1/12 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 1/12 of the mass of an atom of carbon - 12
The relative isotopic mass is the same as which number?
Mass number
Which 2 assumptions are made when calculating mass number?
1- 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 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 sample 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 elections?
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 is the charge of an ammonium ion?
+1 → NH4 ^+
What is the charge of a hydroxide ion?
-1→ OH^-
What are molecular ions?
Covalently bonded atoms that lose or gain electrons
What is the charge of a nitrate ion?
-1 → NO3^-
What is the charge of a carbonate ion?
-2 → CO3^2-
What is the change of sulphate 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
