Atoms and Atomic Structure

To find the number of atoms in 11.5 g of mercury (Hg), first determine the number of moles using its molar mass, which is approximately 200.59 g/mol. Divide the mass by the molar mass: ( 11.5 , \text{g} \div 200.59 , \text{g/mol} \approx 0.0573 , \text{mol} ). Then, multiply the number of moles by Avogadro's number ( (6.022 \times 10^{23} , \text{atoms/mol}) ): ( 0.0573 , \text{mol} \times 6.022 \times 10^{23} \approx 3.45 \times 10^{22} ) atoms. Thus, there are approximately ( 3.45 \times 10^{22} ) atoms in 11.5 g of Hg.

Elements that are likely to be the least reactive are those found in Group 18 of the periodic table, known as the noble gases. These elements, such as helium, neon, and argon, have a full outer shell of valence electrons (eight, in most cases), making them stable and less likely to engage in chemical reactions. Additionally, elements with a full outer shell, like the alkaline earth metals in Group 2, are also generally less reactive than those with fewer valence electrons.

The n=2 electron shell can hold a maximum of 8 electrons. This is determined by the formula 2n², where n is the principal quantum number. For n=2, the calculation is 2(2)² = 8. Thus, the n=2 shell can accommodate up to 8 electrons in total.

Carbon atoms can gain or lose electrons, but they typically do not do so easily because they have four valence electrons. This configuration allows carbon to form stable covalent bonds with other atoms rather than becoming charged ions. Gaining or losing electrons would require significant energy input or release, which is not favorable for carbon under normal conditions. Instead, carbon most commonly participates in sharing electrons to achieve a full outer shell through covalent bonding.

An atom is smaller than a molecule. Atoms are the basic building blocks of matter and consist of protons, neutrons, and electrons. Molecules, on the other hand, are formed when two or more atoms bond together. Therefore, a molecule is made up of one or more atoms, making it larger than a single atom.

An electron cannot gain or lose electrons because it is a fundamental subatomic particle with a fixed negative charge. Instead, electrons can be transferred between atoms or molecules, causing some atoms to become positively charged (when they lose electrons) and others to become negatively charged (when they gain electrons). In this context, the behavior of electrons is determined by their interactions with other particles rather than changing their own quantity.

When a parent nuclide emits an alpha particle, which consists of 2 protons and 2 neutrons, the mass number (A) of the nuclide decreases by 4, as it loses a total of 4 nucleons. The atomic number (Z) decreases by 2 because the emission of 2 protons reduces the number of protons in the nucleus. As a result, the parent nuclide transforms into a different element that is two positions to the left on the periodic table.

The electron configuration of potassium (K), which has an atomic number of 19, in long form is 1s² 2s² 2p⁶ 3s¹. In short form, it can be represented as [Ar] 4s¹, where [Ar] denotes the electron configuration of argon, the nearest noble gas preceding potassium.

The diameter of a carbon atom, including its outer electrons, is approximately 0.3 to 0.5 nanometers (3 to 5 angstroms). This measurement varies slightly depending on the specific model used to represent the atom, as electron clouds are not fixed and can fluctuate. In general, the atomic size reflects the space occupied by the electron cloud surrounding the nucleus.

An ion that has lost electrons and has a net positive charge is called a cation. Cations are formed when atoms or molecules lose one or more electrons, resulting in an excess of protons compared to electrons. This positive charge can occur in various elements, particularly metals, which tend to lose electrons easily. Examples of cations include sodium (Na⁺) and calcium (Ca²⁺).

Phosphorus (P), with an atomic number of 15, has 15 electrons. The electron distribution follows the order of filling energy levels: 2 electrons in the first shell, 8 in the second shell, and 5 in the third shell. This can be represented as 1s² 2s² 2p⁶ 3s² 3p³, indicating that phosphorus has five valence electrons in its outermost shell, contributing to its chemical reactivity.

If an atom does not have enough electrons, it becomes positively charged and is referred to as a cation. This can occur when an atom loses one or more electrons during chemical reactions, leading to an imbalance between the number of protons (positive charge) and electrons (negative charge). As a result, the atom may seek to gain electrons from other atoms or molecules to achieve a more stable electronic configuration.

Copper has more protons than carbon. Carbon has 6 protons, while copper has 29 protons. Therefore, copper is the element with the greater number of protons.

The spdfg subshells can hold a total of 32 electrons. The distribution is as follows: the s subshell holds 2 electrons, the p subshell holds 6 electrons, the d subshell holds 10 electrons, the f subshell holds 14 electrons, and the g subshell can hold 18 electrons. Therefore, when all subshells are filled, they collectively accommodate 2 + 6 + 10 + 14 + 18 = 50 electrons.

In an electron dot diagram, the number of dots surrounding an atom represents its valence electrons. Each pair of dots can form a bond, meaning that the number of bonding pairs (dots that are shared between atoms) indicates how many bonds the atom can form. For example, if an atom has four valence electrons, it can form up to four covalent bonds by sharing those electrons. Thus, the arrangement of dots directly relates to the bonding capacity of the atom.

Two different molecular forms of the same element in the same physical state are oxygen (O₂) and ozone (O₃). Both exist as gases at room temperature but have different molecular structures and properties. O₂ is essential for respiration and combustion, while O₃ plays a crucial role in absorbing harmful ultraviolet radiation in the Earth's stratosphere. These molecular variations illustrate the concept of allotropy, where elements can exist in multiple structural forms.

To draw the Lewis structure for CuBr₂, start by determining the total number of valence electrons. Copper (Cu) has one valence electron, and each bromine (Br) has seven, giving a total of 15 valence electrons. In CuBr₂, copper donates its single electron to form a +2 oxidation state, allowing it to bond with two bromine atoms, each sharing one of their electrons. The structure will show Cu at the center with two Br atoms connected by single bonds, and each Br will have three lone pairs of electrons around it to fulfill the octet rule.

Electrons are the particles that orbit around the nucleus of an atom. They are negatively charged and occupy specific energy levels or orbitals surrounding the positively charged nucleus, which contains protons and neutrons. The behavior of electrons is described by quantum mechanics, which defines their probable locations rather than fixed paths.

When there is unequal sharing of electrons between two atoms in a bond, it is known as a polar covalent bond. In this type of bond, one atom has a stronger electronegativity, causing it to attract the shared electrons more closely, resulting in partial positive and negative charges on the atoms. This uneven distribution of electron density creates a dipole moment in the molecule.

The element cesium (Cs) has an atomic number of 55, which means it has 55 protons in its nucleus, regardless of the isotope. The isotope 133Cs specifically indicates that it has 133 nucleons (protons + neutrons), but the number of protons remains the same at 55. Therefore, 133Cs contains 55 protons.

To find the number of neutrons in an atom, you subtract the atomic number (which represents the number of protons) from the mass number (the total number of protons and neutrons). The formula is: Number of Neutrons = Mass Number - Atomic Number. This calculation gives you the number of neutrons present in the nucleus of the atom.

When atoms of different elements join and react together, they form chemical compounds through various types of bonds, such as ionic or covalent bonds. This process often involves the rearrangement of electrons, allowing the atoms to achieve a more stable electron configuration. The resulting compounds exhibit unique properties that differ significantly from the individual elements. Such reactions are fundamental to the formation of the diverse materials and substances found in nature.

In a neutral atom of calcium-41 (⁴¹Ca), the atomic number of calcium is 20, which means it has 20 protons and 20 electrons. The mass number is 41, which represents the total number of protons and neutrons. To find the number of neutrons, subtract the number of protons from the mass number: 41 - 20 = 21 neutrons. Thus, ⁴¹Ca has 20 protons, 21 neutrons, and 20 electrons.

The oxidation number reflects the degree of oxidation of an atom in a compound, indicating whether it has a tendency to lose or gain electrons. An atom with a positive oxidation number typically indicates a tendency to lose electrons, as it has fewer electrons than protons, while an atom with a negative oxidation number suggests a tendency to gain electrons, as it has more electrons than protons. Therefore, a higher oxidation number generally implies electron loss, while a lower or negative oxidation number suggests electron gain. This behavior influences the type of bonding and the reactivity of the atom in chemical reactions.

In a neutral object, the number of electrons is equal to the number of protons. This balance ensures that the overall electric charge of the object is zero, as the positive charge of protons cancels out the negative charge of electrons. Thus, in a neutral state, the electrical forces are balanced, leading to no net charge.