A water molecule (H₂O) consists of two hydrogen atoms and one oxygen atom. Here's a detailed description of its atomic structure and chemical bonds:
Atomic Structure
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Oxygen Atom:
- The oxygen atom is at the center of the water molecule. It has an atomic number of 8, which means it has 8 protons and typically 8 neutrons in its nucleus (though isotopes can vary this number slightly). The electron configuration of oxygen is 1s² 2s² 2p⁴, meaning it has a total of 8 electrons: 2 in the innermost shell (1s) and 6 in the outer shell (2s and 2p).
- The oxygen atom has six valence electrons (the electrons in the outermost shell), allowing it to form two covalent bonds.
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Hydrogen Atoms:
- Each hydrogen atom has an atomic number of 1, meaning it has 1 proton and typically 0 neutrons. Its electron configuration is simply 1s¹, indicating it has one electron in its outer shell (which is also its only shell).
- Each hydrogen atom has one valence electron and tends to form one bond.
Chemical Bonds
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Covalent Bonds:
- The bonds that hold the water molecule together are known as covalent bonds. In the water molecule, each hydrogen atom shares its single electron with the oxygen atom. Consequently, the oxygen atom shares one of its six valence electrons with each hydrogen atom, resulting in two covalent bonds.
- This sharing of electrons allows all three atoms to achieve greater stability, with the hydrogen atoms filling their outer shell (which is satisfied with two electrons) and the oxygen atom filling its outer shell with a total of eight electrons through these bonds.
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Molecular Geometry:
- The water molecule has a bent or V-shaped geometry due to the two hydrogen atoms being positioned at an angle relative to the oxygen atom. The angle is approximately 104.5 degrees. This shape is a consequence of the two lone pairs of electrons on the oxygen atom, which repel the bonding pairs of electrons.
Polarity of Water
- Water is a polar molecule because of the difference in electronegativity between oxygen and hydrogen. Oxygen is more electronegative, meaning it attracts the shared electrons more strongly than hydrogen. This leads to a partial negative charge (δ-) near the oxygen and partial positive charges (δ+) near the hydrogen atoms, making water a polar molecule. This polarity is responsible for many of water's unique properties, including its solvent capabilities and high surface tension.
In summary, a water molecule consists of one oxygen atom covalently bonded to two hydrogen atoms, forming a bent molecular structure with polar characteristics.