To draw the Lewis structure for carbonic acid (H2CO3), we start by determining the total number of valence electrons. Carbon (C) has 4 valence electrons, each oxygen (O) has 6, and hydrogen (H) has 1. For H2CO3:
– Carbon: 1 × 4 = 4
– Oxygen: 3 × 6 = 18
– Hydrogen: 2 × 1 = 2
Adding these, we get a total of 4 + 18 + 2 = 24 valence electrons.
Next, we place the atoms. Carbon will be the central atom, flanked by three oxygens, and hydrogen atoms will be bonded to the oxygens. One oxygen will have a double bond with carbon, while the other two will have single bonds, each one bonded to a hydrogen atom:
H H | | O=C ---- O | O
In this configuration, each atom achieves a full outer shell. The oxygen atoms connected by single bonds will have a lone pair of electrons each. The double-bonded oxygen does not have any lone pairs. This Lewis structure shows the distribution of electrons and helps in understanding the molecular structure of H2CO3.