Chapter 8: Problem 84
Use the octet rule to predict the formula of the simplest compound formed from hydrogen and (a) selenium, (b) arsenic, and (c) silicon.
Short Answer
Expert verified
The simplest compounds that hydrogen forms with (a) selenium, (b) arsenic, and (c) silicon are H2Se, H3As, and SiH4, respectively.
Step by step solution
01
Understanding the Octet Rule
The octet rule is a chemical rule that reflects the observation that atoms of main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electron configuration as a noble gas. Hydrogen is an exception, as it achieves stability with two electrons.
02
Determining the Valence Electrons for Hydrogen and Group 16 Element (Selenium)
Hydrogen (H) has one valence electron and needs one more electron to complete its duplet. Selenium (Se) as a group 16 element has six valence electrons and needs two more electrons to complete its octet.
03
Predicting the Formula for Hydrogen and Selenium (H & Se)
Since hydrogen needs one electron to achieve a stable configuration and selenium can accept two hydrogen electrons, two hydrogen atoms will pair with one selenium atom to form H2Se.
04
Determining the Valence Electrons for Hydrogen and Group 15 Element (Arsenic)
Arsenic (As) is a group 15 element with five valence electrons and needs three more electrons to complete its octet.
05
Predicting the Formula for Hydrogen and Arsenic (H & As)
Three hydrogen atoms can provide the three electrons arsenic needs to complete its octet, thus forming H3As.
06
Determining the Valence Electrons for Hydrogen and Group 14 Element (Silicon)
Silicon (Si) is a group 14 element with four valence electrons and also requires four more electrons to complete its octet.
07
Predicting the Formula for Hydrogen and Silicon (H & Si)
Four hydrogen atoms will each share one electron with silicon to fulfill the octet rule, resulting in the formula H4Si, which is more commonly written as SiH4.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chemical Bonding
Chemical bonding is a fundamental concept in chemistry that explains how atoms combine to form compounds. It involves the interaction between the valence electrons of different atoms, which can result in the transfer or sharing of electrons. Bonds are typically categorized into three main types: ionic, covalent, and metallic.
In an ionic bond, one atom donates electrons to another, resulting in the formation of positively and negatively charged ions that attract each other. Covalent bonding occurs when atoms share pairs of electrons, and metallic bonding is characterized by a 'sea' of delocalized electrons shared between many metal ions.
In the case of compounds formed between hydrogen and other nonmetals like selenium, arsenic, and silicon, covalent bonding is the primary interaction. Through covalent bonding, atoms achieve stable electron configurations by sharing electrons, fulfilling the octet rule (or duplet rule for hydrogen). This results in the formation of stable molecules with specific ratios of atoms, as predicted using the octet rule in the exercise.
In an ionic bond, one atom donates electrons to another, resulting in the formation of positively and negatively charged ions that attract each other. Covalent bonding occurs when atoms share pairs of electrons, and metallic bonding is characterized by a 'sea' of delocalized electrons shared between many metal ions.
In the case of compounds formed between hydrogen and other nonmetals like selenium, arsenic, and silicon, covalent bonding is the primary interaction. Through covalent bonding, atoms achieve stable electron configurations by sharing electrons, fulfilling the octet rule (or duplet rule for hydrogen). This results in the formation of stable molecules with specific ratios of atoms, as predicted using the octet rule in the exercise.
Valence Electrons
Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding. They are the electrons that engage in bond formation and are responsible for the chemical properties of an element. The number of valence electrons an atom has determines how it will bond with other atoms.
For example, hydrogen has one valence electron and seeks to gain one more to achieve the stable configuration of helium, its nearest noble gas. On the other hand, elements like selenium, arsenic, and silicon have six, five, and four valence electrons, respectively, and they need additional electrons to reach the nearest noble gas' electron configuration. This number of additional electrons required reflects how many bonds the atoms can form to complete their octet or duplet, as demonstrated in the textbook exercise.
Understanding the concept of valence electrons also helps us predict the reactivity of an element, its bonding capacity (its valency), and the type of ions it will form if it gains or loses electrons during bond formation.
For example, hydrogen has one valence electron and seeks to gain one more to achieve the stable configuration of helium, its nearest noble gas. On the other hand, elements like selenium, arsenic, and silicon have six, five, and four valence electrons, respectively, and they need additional electrons to reach the nearest noble gas' electron configuration. This number of additional electrons required reflects how many bonds the atoms can form to complete their octet or duplet, as demonstrated in the textbook exercise.
Understanding the concept of valence electrons also helps us predict the reactivity of an element, its bonding capacity (its valency), and the type of ions it will form if it gains or loses electrons during bond formation.
Electron Configuration
Electron configuration describes the arrangement of electrons in the orbitals of an atom. The most stable arrangement is when electrons fill the lowest available energy levels before occupying higher levels. These configurations can be predicted using principles such as Aufbau's principle, the Pauli exclusion principle, and Hund's rule.
Under the octet rule, atoms tend to fill or half-fill their valence shell, aiming for a configuration similar to that of the noble gases, which are especially stable due to their complete valence shells. Hydrogen, as an exception, conforms to a duplet rule, achieving stability with just two electrons.
The exercise demonstrates how the electron configuration of atoms directs the formation of chemical compounds. Silicon, for instance, with four valence electrons, shares each one with a hydrogen atom (which has only one valence electron) to form SiH4. This sharing results in a full valence shell for silicon and two electrons for hydrogen, echoing the stable electron configurations of noble gases.
Under the octet rule, atoms tend to fill or half-fill their valence shell, aiming for a configuration similar to that of the noble gases, which are especially stable due to their complete valence shells. Hydrogen, as an exception, conforms to a duplet rule, achieving stability with just two electrons.
The exercise demonstrates how the electron configuration of atoms directs the formation of chemical compounds. Silicon, for instance, with four valence electrons, shares each one with a hydrogen atom (which has only one valence electron) to form SiH4. This sharing results in a full valence shell for silicon and two electrons for hydrogen, echoing the stable electron configurations of noble gases.
