Lecture 1 Flashcards
-Atomic number+ Atomic Mass -Isotopes -Lewis Structure - Octet rule -Covalent and Ionic Bonding
Arrangement of elements in the periodic table is based on ……
Reactivity which is determined by valence electrons
What is the atomic number?
Number of protons in the nucleus- in neutral atoms is same as number of electrons.
What is the mass number
Number of protons and neutrons (nucleons) in the nucleus
What property is determined by mass number?
Physical properties
What property is determined by electrons?
Chemical reactivity
Why is mass number not a whole number?
Elements vary in number of neutrons (isotopes) abundance is calculated
Define isotope
Atoms with same number of protons different number of neutrons
What are the 3 isotopes of H?
Protium H
Deuterium 2H
Tritium 3H
Which isomer of hydrogen is reactive?
Tritium
Define Radioisotope
Radioactive isotope it breaks down
Why do radioisotopes breakdown
Due to unstable nuclei
Unstable ratio of protons: neutrons
Define Half Life
Time taken for activity of a radioactive substance to 1/2 as a result of radioactive decay
What is it meant by “half life of tritium is 12.32yrs”?
Half of tritium will degrade in 12.32 yrs
How to calculate molecular mass
Sum of atomic masses in a molecule
Why is CDCL3 used as NMR solvent and not CHCl3?
What is the difference of C14 with the other isotopes?
-Radioactive form (unstable nuclei)
- trace amounts
Uses of C14
Carbon dating
Explain carbon dating
Why is c14 suitable?
What does degenerate mean?
Orbitals have same energy level
Rules for writing electronic configurations
- Max 2e in each orbital
- e have opposite spins
- e fill empty degenerate orbitals before start pairing
Why e don’t repel each other in orbitals?
e have opposite spins so produce opposite magnetic fields so e attract each other
What does the lewis symbol represent?
Represents valence electrons as dots
Valence electron means
Electrons in the outermost shell
Can group number be used to calculate valency
Group number= valency number
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
Why are noble gases unreactive?
Have full, stable electronic shell- octet rule met
Medical uses of Xenon
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
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
