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Understand how nonmetal atoms share electrons to achieve stability.
Why doesn't the water in your glass spontaneously turn into hydrogen and oxygen gas? It’s because the atoms are locked in a microscopic 'handshake' so strong that they refuse to let go.
In the world of chemistry, atoms want to be stable, which usually means having a full outer shell of valence electrons. In ionic bonding, one atom 'steals' an electron from another. However, in covalent bonding, neither atom is strong enough to take the electron away. Instead, they share them. Think of it like two people sharing a book because neither can afford to buy it alone; as long as they stay together, they both get to 'read' (or use) the electrons to feel complete. This sharing creates a strong link called a covalent bond.
Let's look at Hydrogen (). 1. A single Hydrogen atom has only valence electron, but it needs to be stable. 2. When two Hydrogen atoms meet, they each bring their electron to the middle. 3. They now share that pair, so both atoms can 'count' electrons in their shell. 4. This shared pair is written as .
Quick Check
In a covalent bond, do atoms give away their electrons or keep them in a shared space?
Answer
They keep them in a shared space so both atoms can use them.
Covalent bonds almost always happen between nonmetals. Nonmetals (like Carbon, Nitrogen, and Oxygen) have high electronegativity, meaning they have a strong 'hunger' for electrons. Because they both want to pull electrons in, they end up in a chemical tug-of-war where nobody wins, resulting in a tie—the shared bond. This is why the air you breathe ( and ) and the DNA in your cells are held together by covalent bonds rather than ionic ones.
Water () is a classic covalent molecule. 1. Oxygen has valence electrons and needs more to reach the 'magic number' of . 2. Two Hydrogen atoms each have electron to offer. 3. Oxygen shares one electron with the first Hydrogen and another with the second. 4. This creates two single bonds, resulting in a stable structure.
Quick Check
Which group of elements on the periodic table is most likely to form covalent bonds with each other?
Answer
Nonmetals.
Most atoms follow the Octet Rule, which states they are most stable when they have electrons in their outer shell. A single covalent bond consists of exactly one pair (two electrons) being shared. By sharing, atoms can fill their 'empty seats' without needing to find extra electrons from nowhere. If an atom needs three electrons to be full, it might form three separate single bonds with three different atoms.
Methane () shows how one atom can satisfy many others. 1. Carbon has valence electrons; it needs more to reach . 2. Four Hydrogen atoms arrive, each needing electron. 3. Carbon forms a single covalent bond with each of the four Hydrogens. 4. Total electrons for Carbon: (original) + (shared) = . Everyone is stable!
Which of the following pairs would most likely form a covalent bond?
How many total electrons are shared in a single covalent bond?
In a covalent bond, one atom becomes positively charged and the other becomes negatively charged because electrons are transferred.
Review Tomorrow
In 24 hours, try to explain the 'Octet Rule' to a friend and draw a simple diagram of two Fluorine atoms () sharing electrons.
Practice Activity
Look at a periodic table and pick two nonmetals. Based on their group number, can you predict how many electrons they need to share to become stable?