Lecture 1: Introduction & Chemical Bonds Flashcards
What is the nucleus made up of?
Protons and Neutrons
How many protons does an atom with 6 electrons have?
6 protons(atoms have the same number of protons and electrons)
What is the atomic number?
The number of protons in a specific elements atom(this is how elements identify)
What is the mass number?
The number of protons plus the number of neutrons
Atomic Mass vs Mass Number
Mass Number: Number of protons and neutrons in an atom
Atomic Mass: The average number of protons and neutrons for all natural isotopes of an element.
What is the atomic mass?
The average number of protons and neutrons for all natural isotopes of an element.
What is an isotope?
Two atoms of the same element that have the same number of protons but differ in neutrons.
Isotopes with neutrons
Are more unstable(radioactive) and due to that are important in biology and medicine
Rows in the periodic table
Elements all have their electrons in the same shell and are all similar sizes
Columns in the periodic table
Elements have the same number of valence electrons and have similar chemical properties
Covalent Bonds
- Molecules
- Two atoms share electrons
Non-polar Covalent Bond
Electrons are equally distributed between the two atoms
Polar Covalent Bond
Electrons are unequally distributed between two atoms(due to difference in electronegativity)
Hydrogen Bond
Polar covalent bond between hydrogen and N, O or F (caused by large difference in electronegativity)
Which is stronger the covalent bond or the hydrogen bond?
Covalent bond
Water molecules and hydrogen bonding
Hydrogen bonds form between H2O molecules. This creates a network of hydrogen bonds which has a large overall strength
Why can spiders walk on water?
Spiders can walk on water because of the network of hydrogen bonds that is strong enough to support small animals(surface tension)
Four phenomena that result from hydrogen bonding between water molecules
- Surface tension
- Meniscus
- Ice
- Chemical Reactions
Why does a meniscus form when water is poured into a glass?
Water molecules at the surface experience a downward pull from water molecules below, to counteract this the water molecules will adhere to the sides of the glass to resist the downward pull
How does water travel up tree trunks?
Evaporation occurs at the top of the tree pulling all of the water molecules up the tree since they are all bonded together
Is ice more dense than liquid water?
No, liquid water is more dense than frozen water
Two most common elements in biology?
- Hydrogen
- Carbon
Unit for atomic mass and why is can’t be gram?
Unit: Daltons(D)
Can’t be grams because the number would be EXTREMELY small
What determines the shape of a molecule?
The shape of the orbitals
What is electronegativity?
Measure of how strongly electrons are attracted to the nucleus
What elements are more electronegative?
Elements with more protons are more electronegative
Why do electrons determine the ability of atoms to combine with other atoms?
Only electrons are involved in bonds. Hence the distribution and the amount of electrons available for interaction is critical for atoms to combine with other atoms.
