Lecture 1 Flashcards

-Atomic number+ Atomic Mass -Isotopes -Lewis Structure - Octet rule -Covalent and Ionic Bonding

1
Q

Arrangement of elements in the periodic table is based on ……

A

Reactivity which is determined by valence electrons

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2
Q

What is the atomic number?

A

Number of protons in the nucleus- in neutral atoms is same as number of electrons.

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3
Q

What is the mass number

A

Number of protons and neutrons (nucleons) in the nucleus

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4
Q

What property is determined by mass number?

A

Physical properties

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5
Q

What property is determined by electrons?

A

Chemical reactivity

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6
Q

Why is mass number not a whole number?

A

Elements vary in number of neutrons (isotopes) abundance is calculated

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7
Q

Define isotope

A

Atoms with same number of protons different number of neutrons

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8
Q

What are the 3 isotopes of H?

A

Protium H
Deuterium 2H
Tritium 3H

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9
Q

Which isomer of hydrogen is reactive?

A

Tritium

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10
Q

Define Radioisotope

A

Radioactive isotope it breaks down

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11
Q

Why do radioisotopes breakdown

A

Due to unstable nuclei
Unstable ratio of protons: neutrons

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12
Q

Define Half Life

A

Time taken for activity of a radioactive substance to 1/2 as a result of radioactive decay

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13
Q

What is it meant by “half life of tritium is 12.32yrs”?

A

Half of tritium will degrade in 12.32 yrs

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14
Q

How to calculate molecular mass

A

Sum of atomic masses in a molecule

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15
Q

Why is CDCL3 used as NMR solvent and not CHCl3?

A
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16
Q

What is the difference of C14 with the other isotopes?

A

-Radioactive form (unstable nuclei)
- trace amounts

17
Q

Uses of C14

A

Carbon dating

18
Q

Explain carbon dating
Why is c14 suitable?

19
Q

What does degenerate mean?

A

Orbitals have same energy level

20
Q

Rules for writing electronic configurations

A
  • Max 2e in each orbital
  • e have opposite spins
  • e fill empty degenerate orbitals before start pairing
21
Q

Why e don’t repel each other in orbitals?

A

e have opposite spins so produce opposite magnetic fields so e attract each other

22
Q

What does the lewis symbol represent?

A

Represents valence electrons as dots

23
Q

Valence electron means

A

Electrons in the outermost shell

24
Q

Can group number be used to calculate valency

A

Group number= valency number

25
What does the Octet rule state?
Atoms gain/ lose e to obtain noble gas electronic configuration( usually 8e) So they get a stable full shell
26
Why are noble gases unreactive?
Have full, stable electronic shell- octet rule met
27
Medical uses of Xenon
28
What is ionic bonding? Which type of atoms form ionic bond? Property of ionically bonded structures
Electrostatic force of attraction b/w cation and anion creat solid crystal structures with high mp and bp
29
What is covalent bonding? Which type of atoms form covalent compounds? Structure of covalent compounds
Sharing pair of e b/w 2 non metals Molecules with low mp and bp are produced