The number of species from the following in which the central atom uses $\mathrm{sp}^3$ hybrid orbitals in its bonding is __________.

$$\mathrm{NH}_3, \mathrm{SO}_2, \mathrm{SiO}_2, \mathrm{BeCl}_2, \mathrm{CO}_2, \mathrm{H}_2 \mathrm{O}, \mathrm{CH}_4, \mathrm{BF}_3$$

<p>To determine the number of species in which the central atom uses $\mathrm{sp}^3$ hybrid orbitals in its bonding, we need to analyze the hybridization of each central atom in the given species.</p> <p>1. <strong>$\mathrm{NH}_3$ (Ammonia)</strong>:</p> <p>The central atom is nitrogen. Ammonia has 3 sigma bonds and 1 lone pair. Thus, the steric number is 4, which corresponds to $\mathrm{sp}^3$ hybridization.</p> <p>2. <strong>$\mathrm{SO}_2$ (Sulfur dioxide)</strong>:</p> <p>The central atom is sulfur. Sulfur dioxide has 2 sigma bonds and 1 lone pair. Thus, the steric number is 3, which corresponds to $\mathrm{sp}^2$ hybridization.</p> <p>3. <strong>$\mathrm{SiO}_2$ (Silicon dioxide)</strong>:</p> <p>The central atom is silicon. Silicon dioxide has a linear structure with double bonds, leading to $\mathrm{sp}$ hybridization.</p> <p>4. <strong>$\mathrm{BeCl}_2$ (Beryllium chloride)</strong>:</p> <p>The central atom is beryllium. Beryllium chloride has 2 sigma bonds and no lone pair. Thus, the steric number is 2, which corresponds to $\mathrm{sp}$ hybridization.</p> <p>5. <strong>$\mathrm{CO}_2$ (Carbon dioxide)</strong>:</p> <p>The central atom is carbon. Carbon dioxide has a linear structure with double bonds, leading to $\mathrm{sp}$ hybridization.</p> <p>6. <strong>$\mathrm{H}_2\mathrm{O}$ (Water)</strong>:</p> <p>The central atom is oxygen. Water has 2 sigma bonds and 2 lone pairs. Thus, the steric number is 4, which corresponds to $\mathrm{sp}^3$ hybridization.</p> <p>7. <strong>$\mathrm{CH}_4$ (Methane)</strong>:</p> <p>The central atom is carbon. Methane has 4 sigma bonds and no lone pair. Thus, the steric number is 4, which corresponds to $\mathrm{sp}^3$ hybridization.</p> <p>8. <strong>$\mathrm{BF}_3$ (Boron trifluoride)</strong>:</p> <p>The central atom is boron. Boron trifluoride has 3 sigma bonds and no lone pair. Thus, the steric number is 3, which corresponds to $\mathrm{sp}^2$ hybridization.</p> <p>From the above analysis, the species in which the central atom uses $\mathrm{sp}^3$ hybrid orbitals are:</p> <ul> <li>$\mathrm{NH}_3$</li> <li>$\mathrm{H}_2\mathrm{O}$</li> <li>$\mathrm{CH}_4$</li> </ul> <p>Therefore, the number of species where the central atom uses $\mathrm{sp}^3$ hybrid orbitals is <b>3</b>.</p>