Atomic Structure (Alan's Notes) Flashcards
What is a covalent bond?
Covalent bonds are where non-metals share electrons and create a covalently bonded molecule.
What makes a noble gas stable?
The amount of electrons in the outer shell. 8 electrons is a stable amount.
What is a molecule?
It consists of two or more atoms bonded together by covalent bonds.
List examples of Diatomic gases.
O2, Cl2, S2, N2.
What are atoms composed of?
Protons, neutrons and electrons.
When does the number of protons equal the number of electrons?
In an electrically neutral atom.
Define isotopes.
They are atoms of the same element that have different numbers of neutrons in the nucleus.
What are ions?
Ions are charged atoms.
- Positive ions have more protons than electrons.
- Negative ions have more electrons that’s protons.
What are valence electrons?
They are electrons in the outermost shell of an atom.
How are the elements arranged in the periodic table?
They are arranged in order of increasing atomic number.
What are periods?
They are horizontal rows of elements in the periodic table.
What are groups?
They are vertical columns of elements in the periodic table.
•Elements in the same group in the periodic table have the same outer-shell electron arrangement and they share some similar properties.
What are the trends in the 1st Ionisation energy?
- The atoms nuclear charge
- The distance between the nucleus and outermost electrons - ATOMIC RADIUS
- Shielding by inner electrons
What does the trends in the 1st Ionisation energy have to do with the atoms nuclear charge?
- Depends upon it’s # of protons
- Increasing nuclear charge means electrons are attracted more strongly to the nucleus and so Ionisation energy increases with increasing nuclear charge.
What does the trends in the 1st Ionisation energy have to do with the distance between the nucleus and outermost electron - ATOMIC RADIUS?
- As the atomic radius increases so the strength of attraction between the nucleus (+) and the outer electron (-) decreases.
- Thus Ionisation energy decreases with increasing atomic radius.
What does the trends in the 1st Ionisation energy have to do with the shielding by inner electrons?
- Each electron in the atoms electron cloud repels each other.
- The more electrons there are between the outer electrons and the nucleus the more easily the electron is removed and the lower the Ionisation energy.
When does successive Ionisation energies increase for an atom?
- Gradually as the charge in the ion being formed increases.
* Markedly when the electron is removed from a shell closer to the nucleus.
How is the core charge determined?
It is determined by subtracting the number of inner-shell electrons from the number of protons in the nucleus.
What do the atomic radius, Ionisation energy and electronegativity of an element depend on?
They depend on the core charge experienced by the outermost electrons and the average distance of these outermost electrons from the nucleus.
What is the atomic radius?
It is a measure of the size of its atom usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons.
How is the elements on a periodic table arranged according to it’s atomic radius?
They increase down a group and decrease across a period.
What causes an unusual decrease in the atomic radius? (Elements further to the right of the period)
Higher nuclear charge increases the attraction of electrons bringing them closer to the nucleus thus resulting in a decreased in atomic radius.
What causes the increase in atomic radius down a group?
It is due to the higher shell number of the outer electrons for elements lower in a group.
• Electrons in higher shells are generally further away from the nucleus and this causes the atoms further down a group to have a larger radius.
What is the atomic radius of a metal defined as?
Being half the distance between the centres of two adjacent atoms in the metallic lattice.
What is the atomic radius for non metal atoms that form diatomic molecules?
It is half the distance between the centres of two bonded atoms.
Define Ionisation energy.
It is the energy required to remove the most loosely bound electron from an atom, in the gaseous phase.
How does the Ionisation of energy work?
It meanders the minimum amount of energy needed to remove the single most loosely bound electron from an atom in the neutral gaseous state.
How are the elements arranged according to the first Ionisation energy in the periodic table?
They decease down a group and increase across a period.
Define electronegativity.
The ability of an atom in a molecule to attract electrons to itself.
It is a measure of the electron-attracting power of an atom
in a molecule.
•electronegativity decrease down a group and increases across a period.
Why do non-metal elements generally have the highest values of electronegativity?
This is to be expected as the elements typically gain electrons to form negative ions.
Why do metals have low electronegativity ?
Because within the periodic table there is a general trend of increasing electronegativity from left to right in any period. Down any group the electronegativities show a gradual decrease.
