Chemistry Review Part 1.pdf

Chemistry Review: Part 1  Matter has mass and takes up space. It can exist as a solid, liquid or gas. All matter is composed of elements Element – a pure substance that cannot be broken down into simpler substances The smallest particle of an element is an atom Elements consist of individ...

Chemistry Review: Part 1  Matter has mass and takes up space. It can exist as a solid, liquid or gas. All matter is composed of elements Element – a pure substance that cannot be broken down into simpler substances The smallest particle of an element is an atom Elements consist of individual atoms Atomic Structure: Atoms themselves are composed of small, subatomic particles called protons, neutrons and electrons Name of Particle Location of Particles Charge of Particle Proton Nucleus Positive Neutron Nucleus Neutral Electron Orbits around Nucleus Negative Chemistry of Life There are 92 naturally occurring elements. Matter is therefore composed of 92 different kinds of elements. The following elements make up 98% of the body of organisms: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur, Phosphorus.  Atomic Number = Number of protons = Number of electrons Mass Number = Number of protons + Number of neutrons How many protons and neutrons does the element O (oxygen) have?  Isotope – different forms of the same elements, with different atomic masses (# protons = # electrons but # neutrons vary) Radioisotope – a radioactive isotope of an element The nuclei of some isotopes of an element are unstable and tend to break down, or decay, giving off particles of matter that can be detected as radioactivity Can be used as tracers – gives off a radioactive signal as they decay that are easily detectable in a cell Radioisotopes in Medicine Radioisotope tracing – doctors inject radioactive material into a patient and trace its movement through the body Example: Cancerous tissues in the body have higher levels of activity than healthy tissues - Injecting a patient with radioactive glucose This positron emission tomography and then performing a positron emission (PET) scan is of a 62-year-old man’s tomography (PET) scan is a method to brain. The yellow and orange areas diagnose a cancerous tumour represent a tumour, which breaks down the injected radioactive glucose at a faster rate than normal cells do. Recall: Representations of the Atom  Draw the Lewis Dot Diagrams for Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur, Phosphorus. C H O N S P Energy Levels of Electrons An atom’s electrons vary in the amount of energy they possess Electrons further from the nucleus have more energy Electrons can absorb energy and become “excited” Excited electrons gain energy and jump to higher energy levels. When electrons lose energy, they move back down to lower energy levels Electron Arrangements The chemical behavior of an atom is determined by its electron configuration –that is, the distribution of electrons in the atom’s electron shells. Thechemical behaviour of an atom depends mostly on the number of electrons in its valence orbital All atoms with incomplete valence shells are chemically reactive. Electronshave potential energy because of their Potential energy is the stored position relative to the positively charged nucleus energy that an object possesses due to its relative position to other objects Electron Arrangements Electrons move around the atomic nucleus in specific regions called orbitals Rather than exist in a well-defined circular orbit, electrons occupy three-dimensional orbitals! An orbital is the three-dimensional space where an electron is found 90% of the time. Energy Shells Electron orbitals are grouped into energy levels (energy shells) Lowest energy shell is closest to the nucleus Orbitals can be s, p, d or f shaped and can each hold 2 electrons  Energy Shells 1st electron shell (1s orbital) – single spherical orbital. E.g., H has only a 1s electron orbital containing 1 e-, while He contains 2 electrons in its 1s orbital Shell at the second energy level consists of a 2s orbital and three 2p orbitals - can occupy a spherical orbital (2s), and/or 3 dumbbell shaped (2p) orbitals E.g., Neon has 10 electrons 1s orbital – filled with 2 electrons 2p orbitals – filled with 6 electrons Remember…. First energy level – 2 electrons Second energy level – 8 electrons Third energy level – 18 electrons Electrons further from the nucleus have more energy. The 2p orbitals have a higher energy than the 2s orbital because the 2s is closer to the nucleus Need to review? https://www.youtube.com/watch?v=Ewf7RlVNBSA Structures and Shapes of Molecules Molecular formulas – shows the number of each type of atom in an element or compound e.g., H2O, C6H12O6 Shows number and types of atoms in a molecule Structural formulas – shows how the different atoms of a molecule are bonded together Line is drawn between atoms to indicate a covalent bond  Isomer Two molecules with the same molecular formula but different molecular structure This gives different chemical properties  Ion atoms that have lost or gained electrons and become charged Forces of Attraction Intramolecular forces hold atoms together within a molecule. ○ ionic (metal + non-metal) ○ covalent (2+ nonmetals) These are stronger than intermolecular forces Intermolecular forces-occur between molecules ○ VERY important for holding together strands of DNA and determining the shape of proteins Ionic Bonding Ionic bond – a chemical bond between oppositely charged ions Anion – gained e- therefore is negative Cation – lost e- therefore positive Ionic bonds form in fixed ratios and are generally strong in their crystal from – but are easily broken apart by water – this is significant to biological systems Ionic compounds are called salts Ionic Bonding  Covalent Bonding Atoms share electrons to achieve stable conformations. - This ‘sharing’ can be equal: non-polar bond - This ‘sharing’ can be unequal: polar bond  Ionic vs. Covalent: Electronegativity The measure of the relative abilities of bonding atoms to attract electrons (Pauling Scale) Noble gases are not assigned an En because they do not participate in chemical bonding (EN=0) The difference in electronegativity between two atoms determines the type of bond that will form Eg: NaCl forms an ionic bond because the △EN is greater than 1.8 H20 forms polar covalent bonds because △EN is between 0.4 and 1.8 CH4 forms non-polar covalent bonds because △EN is less than 0.4 Trends Molecular Compounds: Covalent Bonding Molecular compounds form when atoms share electrons in covalent bonds. The more electronegative the atom is, the more strongly is attracts electrons Forms poles (oppositely charged ends) Polarity – partial positive or negative charge at the end of a molecule Polar molecules attract and align themselves to other polar molecules (and tend to be soluble in water)! Why is this important to Biological systems? Large molecules can have polar, and non-polar regions that influence how they “behave” with other molecules  Intermolecular Forces Hydrogen Bonds – the attractive force between a partially positively charged hydrogen atom and a partially negatively charged atom in another molecule occurs between 2 polar molecules weak as a single bond but many are very strong gives water its special properties  Read over your notes Read section 1.1 of the textbook Homework pg. 10-13 Pg. 17 #1, 2, 4, 5, 6