Section One: Atoms and Moles Flashcards
What was stated in Dalton’s atomic theory?
- Atoms are tiny particles made of elements (spheres)
- 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 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?
- 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, neutron, and electron?
P: +1
N: 0
E: -1
Which particle has the same mass as proton?
Neutron
Which two particles make up most of atom’s mass?
Protons and neutrons
What does the atomic number tell about an element?
Atomic number = number of protons in an atom
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 electrons, isotopes have
the same number of electrons in the same
arrangement
what are ions?
Charged particles formed from the loss or gain of electrons in an atom
What is the charge of the ion when electrons are gained? What is the charge of the ion when electrons are lost?
gained: negative
lost: positive
Define relative atomic mass
the weighted mean mass of an atom of an element, compared to 1/12th of the mass of an atom of carbon-12
Define relative isotopic mass
the mass of an atom of an isotope, compared to 1/12th of the mass of an atom of carbon-12
ture of false? The relative isotopic mass is same as the mass number
true
define relative molecular mass (Mr)
the mean mass of a molecule, compared to 1/12th of the mass of an atom of carbon-12
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 is the group number related to the number of electrons?
Group number = number of electrons in
the outer shell
Which are the 4 elements that don’t tend to form ions and why?
- 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 these ions?: ammonium, hydroxide, nitrate, carbonate, sulfate
+1 → NH4
-1 → OH
-1 → NO3
-2 → CO3
-2 → SO4
