A1.1.2.pptx water - hydrogen bonding of water

water

1. A1.1.2 ​Hydrogen bonds as a consequence of the polar covalent bonds within water molecules

2. Atomic Structure An atom is the smallest unit of matter that is unique to a particular element. Our current model of the atom can be broken down into three constituents parts – Protons- carry a positive charge Neutrons - possess no net charge Electrons - have a negative charge Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions .

3. Atoms In accordance with the Standard Model of particle physics, protons and neutrons make up the nucleus of the atom, while electrons orbit it in a "cloud". The electrons in an atom are attracted to the protons in the nucleus by an electromagnetic force in which positive charge attracts negative charge. Electrons orbit the nucleus in multiple orbits. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy. This occurs in photosynthesis (C1.3.9)!

4. Atomic Bonding Electrons may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to form bonds. A chemical bond is an attraction between atoms, ions or molecules that enables the formation of chemical compounds. In IB Biology, the types of “bonds” to know are: Nonpolar covalent bond Polar covalent bond Ionic bond Hydrogen bond (intermolecular force, not a true bond)

5. Covalent Bond A covalent bond holds together two atoms that share one or more pair of electrons between atoms. Nonpolar Covalent Share electrons equally. Nonpolar covalent bonds are common within the many carbon compounds upon which life is based (B1.1.1), such as proteins (B1.2.9) and DNA ( A1.2.3 ). ⚫ is the nucleus of each atom blue is the cloud of electrons shared equally between the two atomic nuclei Polar Covalent Share electrons unequally Polar covalent bonds can occur in amino acid R-groups (B1.2.6) which impacts the tertiary structure of a protein (B1.2.10). Because there are LESS ELECTRONS around this nucleus, there is a slight positive charge ( ઠ + ) on this nucleus ⚫ This nucleus has more pull on the electrons, so it has a bigger electron cloud surrounding it Because electrons have a negative charge and there are MORE ELECTRONS around this nucleus, there is a slight negative charge ( ઠ - ) on this nucleus

6. Ionic Bond An ionic bond is an attraction between a positively charged ion and an negatively charged ion. This atom has lost an electron, making it a positively charged CATION. Example: Na + This atom has gained an electron, making it a negatively charged ANION. Example: Cl - Ionic bond Ionic bonds can occur between amino acids as a polypeptide folds into its tertiary structure to become a functional protein (B1.2.9).

7. Hydrogen Bond A hydrogen is an attraction between two polar molecules. A polar molecule is a molecule in which one end of the molecule is slightly positive, while the other end is slightly negative. The attraction between the slightly positive (ઠ+) and slightly negative (ઠ-) regions of two different polar molecules is called a hydrogen bond. H-bonds are represented with a dotted line. one polar molecule another polar molecule H-bond Hydrogen bonds form between strands of DNA ( A1.2.6 ), allowing for allowing genetic information to be easily replicated ( A1.2.8 ) and expressed (D1.2.2). Hydrogen bonds also maintain the structure of cellulose (B1.1.6) and proteins (B1.2.8 and B1.2.9)

8. W ater Structure A water molecule consists of 2 hydrogen and 1 oxygen atom, hence…H 2 O. Within a water molecule, electrons are shared through polar covalent bonding between the atoms. These electrons🟡are being shared between the O and H, so it’s a covalent bond.

9. Water molecules are polar Because the oxygen atom has more protons, it attracts the shared electrons more of the time creating an unequal distribution of charge. δ+ hydrogens δ- oxygen The shared electrons (and their negative charge) are pulled towards the oxygen.

10. OXYGEN OF WATER MOLECULE the 8 protons in the nucleus of the O-atom have more pull on the shared electrons. HYDROGEN OF WATER MOLECULE the 1 proton in the nucleus of the H-atom has less pull on the shared electrons. the electrons are pulled towards the oxygen atom the rope represents electrons

11. Hydrogen bonds form between water molecules Chemistry Online The many intermolecular hydrogen bonds between water maintain its high heat capacity ( A1.1.6 ) . The partially positive hydrogen atoms of one water molecule are attracted to the partially negative oxygen atom of a different water molecule, forming a hydrogen bond. Each water can form up to H-bonds with up to 4 other water molecules

12. The H-bonds are made and broken quickly as the molecules move, however the large numbers of bonds contribute to the stability and retainment of water on Earth ( A1.1.7* ) Water’s ability to attract polar and charged molecules grants it a number of emergent properties such as cohesion ( A1.1.3 ), adhesion ( A1.1.4 ), solvency ( A1.1.5 & D2.3.1 ) and a high specific heat ( A1.1.6 ). Collectively these property make water the primary medium of life ( A1.1.1 ).

13. © www.biologyforlife.com Before using any of the files available on this site, please familiarize yourself with the Creative Commons Attribution License . ​​It prohibits the use of any material on this site for commercial purposes of any kind. Coffey, J. What are the parts of an atom? Universe Today (2015). Available from: What are the parts of an atom?