1 - Atomic Structure & The Periodic Table Flashcards
(34 cards)
What are the charges and masses of:
- Electrons?
- Protons?
- Neutrons?
• Electrons: - charge = -1 - mass = 0.0005 • Protons: - charge = +1 - mass = 1 • Neutrons: - charge = 0 - mass = 1
How do you work out the amount of neutrons in an atom?
Mass - Atomic Number
What is the difference between ions and isotopes?
Ions have an imbalance of electrons, altering the charge, whereas isotopes have varying amounts of neutrons, altering the mass.
- Ions change electron configurations; isotopes do not
- Isotopes have varying physical properties as the mass changes; ions do not
What is Relative Atomic Mass (Ar)?
The weighted means mass of an atom of an element compared to 1/12th the mass of an atom of Carbon-12.
What is Relative Isotopic Mass?
The mass of an isotope’s atom compared with 1/12th mass of an atom of carbon-12.
How do you calculate Relative Molecular Mass (Mr)?
add up masses of the atoms in the compound - e.g. CO2 = 12 + (16x2) = 44gmol-1
How do you work out Ar from Isotopic abundances?
1.) Mass x Abundance (add all) E.g. 20% of atoms have mass of 10, 80% have mass of 11: (20x10) + (80x11) = 1080 2.) Divide by 100 E.g. 1080/100 = 10.8
How do you work out the Relative Atomic mass from a graph of abundances?
- ) Mass x Abundance (added)
2. ) Divide by the SUM of the total abundances (%)
How can you use mass spectra to identify compounds?
- ) Find Molecular ion peak - furthest right of graph. This is the element’s RMM
- ) Calculate the RMMs of the given group in the question (e.g. Alcohols) until you reach this RMM.
What is an orbital?
Where electrons are within an energy level (though only a rough indication as electrons move randomly)
What is spin pairing?
Electrons spin anticlockwise or clockwise within orbitals. 2 electrons in the same orbital cannot have the same spin, and so are paired with an electron spinning the opposite way
What are the 3 principles for filling orbitals?
- Aufbau: electrons fill LOWEST energy levels first, except for 4s which comes before 3d
- Pauli’s Exclusion: 2 electrons in each orbital as long as they are spin paired
- Hund’s Rule: electrons in same energy level spread out to maximise number of unpaired electrons
Why does the 4s orbital get filled before the 3d orbital?
Because when the sub shell splits it overlaps with the 3d, giving it a higher energy level and meaning it is filled first.
What are the two exceptions to the 4s before 3d principle and why?
- Chromium (Cr)
- Copper (Cu)
Because the electrons in the 4s shell are donated to the 3d shell in order to achieve a more stable arrangement of lower energy (more paired electrons but with lower repulsion)
What is the electromagnetic spectrum, from lowest to highest energy and frequency?
Radio waves, microwaves, infrared, visible light, ultraviolet, xrays, gamma rays
Why does the flame change colour in flame tests?
The heat energy from the flame causes high-speed collisions between atoms, creating energy that excites electrons into a higher energy level. When the electron drops back down to its ground state, a photon of light in the visible range is emitted, creating the coloured flame.
Why is the emission spectrum different for each element?
Every element has a different electron arrangement, this affecting the amount of radiation frequencies emitted or absorbed.
What are the Lyman and Balmer series?
- Lyman: in the ultraviolet region, obtained when an electron drops to its ground state in the 1st orbit
- Balmer: electron dropping to its ground state in the 2nd orbit.
What are the 4 basic principles of energy levels?
- Electrons only exist in fixed orbits or shells
- Each shell has a fixed energy
- Electromagnetic radiation is aborbed or emitted when electrons move between shells
- This radiation has a fixed frequency (because the energy of shells is also fixed)
What is First Ionisation Energy?
The energy required to remove 1 electron from 1 mole of gaseous atoms to produce 1 mole of 1+ gaseous ions.
E(g) -> E+(g) + e-
What four factors affect ionisation energy?
- Distance effect: distance of outer electron from nucleus. Greater = lower attraction = lower ionisation energy
- Shielding effect: number of energy levels surrounding nucleus. More shells = lower attraction = lower IE
- Nuclear Charge Effect: more protons in nucleus = greater nuclear attraction to electrons = higher IE
- Spin Pair Repulsion: negative charges of electrons repel when they have to pair up within an orbital, this lowering IE as it is easier to remove electrons.
What are the trends in first ionisation energy down a group and across a period?
- Down Groups: DECREASES due to increased distance and shielding effect (more energy levels to separate electrons from nucleus)
- Across Periods: INCREASE due to greater nuclear charge effect (more protons)
What is Second Ionisation Energy?
The energy required to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
E+(g) -> E2+(g) + e-
Why do successive ionisation energies increase?
Because after 1st ionisation, you are left with a positive ion, making it harder to remove electrons from it.
