elements, molecules and cells Flashcards
what does the matter surrounding us consist of?
- chemical elements
what is the smallest unit of an element? what does it contain?
- atom
- contains nucleus with protons (+ charge) and neutrons (no charge)
what do electrons do? why is this important
- orbit the nucleus, which is important for atoms combining to form large elements
what is the charge of electrons equal to?
- negative charge of equal absolute value to protons
- ensures that the atom itself is neutral if electron number = proton number
how is electron movement explained?
- sophisticated
- explained in terms of atomic orbitals
what is position of electrons depicted by?
- electron clouds which are denser where it is more likely to encounter electrons and thinner when less likely
how many elements are known to make up organisms? how many make up 97% of mass of biological substance?
- 26 elements
- around six form 97%
what are the abundant elements? what is an exception?
- hydrogen, carbon, nitrogen, oxygen, phosphorus and sulphur
- hydrogen is an exception due to single proton in nucleus
what is the atomic number?
- indicative of the number of protons in the nucleus
what is atomic mass? what is it calculated in?
- mass of one of the elements atoms
- calculated in dalton (1/12th of 12C atom)
why is the atomic mass useful?
- useful in calculating how much there is of a particular element within a substance
what is an isotope?
- two atoms of the same element differ in number of neutrons but same atomic number
how is molecular weight of diverse elements calculated?
- multiply number of atoms by their respective atomic mass and add them together
where do molecules frequently reside?
- in solution of water so its useful to understand their concentration
- express concentration in moles per litre
what is Avogadro’s number?
- mole of substance always equal to atomic mass in grams of the substance
- contains 6.023 x 10^23
what is molarity?
- refers to the number of moles of the substance in a given volume
- e.g., 1 molar glucose= 1 mole of glucose in 1 litre
what can atoms form bonds with?
- atoms with the same or different elements
what does bonding of atoms require?
- at least two electrons which in most cases are contributed mutually by atoms participating
what bond do atoms create?
- when two atoms share electrons it is known as a covalent bond
what is the number of bonds an atom can form determined by?
- distribution of electrons in its atomic orbitals
- known as electronic structure
what are molecules?
- atoms that are joint by covalent bond
what is a compound?
- if molecules of a substance exist of atoms belonging to two elements
what is the difference between organic and inorganic compounds?
-organic compounds contain carbon whereas inorganic don’t e.g. water
what is the difference in charges between molecules and compounds?
- molecules are electrically neutral
- compounds carry electrical charge in the form of ions
what does the little number demonstrate and why is this useful?
- little number shows the number of atoms
- useful in understanding how much there is of a certain compound in a substance
what is the molecular formula?
- gives a complete list of all the atoms in a molecule
- representation of a molecule that uses chemical symbols to indicate the types of atoms followed by subscripts
what is the structural formula?
- details the way in which atoms are connected in compounds via knowing number of bonds that each atom can form
what is an anion?
- carry electrical charge as some atoms are more stable with more electrons than protons
what is an cation?
- carry less electrons than protons so have a positive charge
what does radical mean?
- when a molecule or ion has an unpaired electron
what is polarity?
- what degree it is polar
- affects the physical property of miscibility
what is miscibility?
- its ability to mix with other substances