Week 2 Flashcards
What information can you get from a periodic table
- Atomic Mass. ie. 10 (Ne = Neon) which tells you that there are 10 protons and therefore must have 10 electrons
- Mass Number which is the sum of the proton and neutrons, and which is 20.18 for Neon as given in the periodic table. We know that there are 10 protons and by dividing the number of protons from the Mass (20.18 - 10 = 10) we then know that the number of neutrons for Neon is 10.
Describe what you understand under Electrons
- Electrons are arranged in shells/energy levels/clouds/orbits
- The first shell has up to 2 electrons
- The second shell has up to 8 electrons
- The third shell holds between 8-18 electrons
- The valence shell is the outermost shell of an atom
(NB) What do you understand under valence sell?
The valence shell is the outermost shell of an atom (outer ring of the number of electrons) Valence shells fill up as follows: • 1st shell – two electrons • 2nd shell – 8 electrons • 3rd shell – 8 electrons minimum
Chemistry hierarchy
• MATTER – “stuff” (see, smell, touch etc)
• ELEMENTS – makes up matter and is composed of atoms
• ATOMS – makes up elements and is composed of protons,
neutrons and electrons
Definition of Molecule:
Molecule: ANY two or more atoms held together by chemical bonds
• Ie molecule of an element = two identical atoms (H + H = H2) or (O + O = O2)
• Ie molecule of a compound = two or more different atoms (Na + Cl = NaCl)
Definition of Compound
• Compound: Two or more different kinds of atoms chemically bonded
together (Eg H + Cl = HCl)
How do atoms form these molecules and
compounds?
• A chemical bonds result from electrons of two atoms interacting
• When a valence shell of an atom is not completely full ( then it is unstable) it will often
look to share electrons with others
Types of chemical bonds
• When two atoms share electrons – covalent bond
• If an atom donates an electron to another atom – ionic bond
Atom which donates the electron becomes positively charged —- Cation (+)
Atom which accepts the electron becomes negatively charge —– Anion (-)
(NB) what is cellular respiration?
Glucose + Oxygen become Carbon dioxide + water + ATP
what do Inorganic compounds mean?
• Don’t contain carbon and carbon-hydrogen bonds
- Acids, bases, water and salts
• Water is the most abundant inorganic compound in our bodies
- 60-80% of the volume of living cells
• Why do we have so much water? Why is it useful?
- High heat capacity
- High heat of vaporisation
- Polar solvent properties
- Important reactant
- Cushioning
• Salts
- Salts are ionic compounds
- Contain cations other than H+, and anions other than OH-
- When dissolved in water dissociate into their ions
_ Water simply overcomes the attraction between
the ions
- Eg NaCl, CaCO3, KCl
- All ions are “electrolytes” as they can conduct
electrical charge in solution
_ Important for nerve impulse transmission
Name the Properties of Acids
• Acids and bases are also electrolytes
- Ionise and conduct electricity in solution
• Properties of Acids
- Sour taste
- Dissolves (reacts) with many metals
- Can cause burns
- Releases hydrogen ions when dissolved in water
Name the properties of Bases
Properties of bases
• Bitter taste
• Feel slippery
• Bases are referred to as “proton acceptors”
- Can “take up” or “accept” hydrogen ions (H+) in acceptable amounts
- Common bases include the hydroxides (OH-)
NaOH → Na+ + OH-
- The resulting hydroxyl ion then “accepts” a proton present in the solution
OH- + H+ → H2O- The end result is water and the removal of a proton from the solution
Bases reduce the acidity of solution making them more alkaline
pH scale allows us to measure the concentration of hydrogen ions in solution
• pH stands for “power of hydrogen”
• Measures the relative concentration of H+ ions in a solution
• Ranges from 0-14
• pH of 1 is highly acidic, pH of 7 is neutral, pH 14 strongly basic/alkaline
• pH scale is logarithmic
- Every variation of a single pH unit represents a 10-fold difference in H+
concentration
• A pH of 1 means a 10-fold greater number of H+ ions than a pH of 2
What do you understand under - pH: Acid-base concentration
1 ACIDS
• More hydrogen ions (H+) in solution the more acidic the solution
• The more acidic a solution, the lower the pH
HCl → H+ + Cl
2 BASES
• The higher the concentration of base (ie hydroxyl ions (OH-))
• The more H+ ions are taken out of the solution (ie the lower the conc. of H+)
• The less acidic a solution is, therefore the higher the pH
NaOH → Na+ + OH-
OH- + H+ → H2O
What is an ION
- an Ion is an atom, or a group[ of atoms that have an elactrical chage
- A Positine ION is calld a Cation
- a Negative ion is called an anion
- Polytomic ions is an group of ions that have a charge.