Atomic structure and isotopes Flashcards
(35 cards)
what is an atom?
*include all key parts
the smallest part of an element which can react in a chemical change
describe the structure of an atom
1- small dense nucleus in the center consisting of proton and neutrons
2- in shells around the nucleus, electrons are found
what is atom mostly of?
empty space
what are the relative charge of protons, neutrons and electrons?
proton=+1
neutron=0
electron=-1
what are the relative masses of protons, neutrons and electrons?
proton=1
neutron=1
electron=1/1836
describe a nuclear notation(what each letter as the example mean)
- use the scientific terms
eg: vCx
v-mass number/nucleon number( number of proton and neutrons )
C- symbol of the element
x-atomic number/ proton number
what is the mass number actually?
number of protons and neutrons in the nucleus of an atom
-number of total mass of parts in the element but electrons are so small so they are not considered in the calculations
What is relative atomic mass
The average mass of all the isotopes of the same element when compared to carbon-12
What is the formula to calculate relative atomic mass using percentage abundance of isotopes?
Percentage 1(mass number1)+ percentage 2(mass number 2) / percentage 1 + percentage 2
what does K+1 mean?
the potassium ion as one less electrons than proton or one more proton then electron
what does k-3 mean?
potassium has gained 3 electrons
describe how electron beams react in an electrical field
*cathode ray tube
1- electrons get repelled from the cathode and attracted to the anode
2- the electron deflects towards the positive plate and hit one certain area of the screen making it glow
what is an alpha particle?
helium ion with 0 electrons and therefore acts as a proton
describe how alpha particles react in the gold foil experiment
*2 main answers and explanation
1- alpha particles travel straight and un-deflected as atom is mostly empty space
2- some alpha particles are deflected as a result of
a) repulsion of positive charge of nucleus
b) the nucleus is tightly packed
describe how neutrons react in an electrical field
they travel straight, un-deflected due to no charge
what is effective nuclear charge?
the amount of positive charge felt by electrons in the last shell taking into consideration the shielding effect
how does atomic radius change across a period
and explain
the atomic radius decreases.
As the number of protons increases, the effective nuclear charge of electrons in the last shell increases causing an attraction between the electrons and the nucleus.
how does atomic radius change down the group?
atomic radius increases
The number of protons down the group increases causing electrons to increase too. due to this, there will be more electron shells/energy level, making the atom get bigger
what do elements in the group have the same of related to this topic?
same number of outer electrons therefore same effective nuclear charge which is why nuclear charge is not considered when talking about elements of the same group
what are anions and cations
cations-positive ions
anions- negative ions
how do cations change across the period ?
and explain
they decrease across a period, cations lose electrons leading to greater positive charge across the period causing the effective nuclear charge to increase so more attraction between the electrons and nucleus
* the greater the positive charge, the smaller the radius
how cations change down a group?
and explain
they increase down the group as the energy level/ electron shell increases however nuclear energy remains the same
explain how anions differ from their natural element
they are bigger than their elements because they have more electrons therefore more repulsion between one another. nuclear energy is not taken into consideration as they have the same nuclear charge
explain how anions radius change down the group?
they increase down the group as the electron shell increases causing more repulsion between electrons
