1. The Atom Flashcards
(35 cards)
What is the basic structure of an atom according to Bohr’s atomic theory?
According to Bohr’s atomic theory, an atom is composed of a nucleus at the center and one or more electrons rotating around the nucleus along different energy orbits. The nucleus is primarily composed of protons and neutrons, collectively called nucleons.
How is the electrical charge of the nucleus balanced in an atom?
For an atom of a given element, the number of electrons moving around the nucleus equals the number of protons, balancing the electrical charge of the nucleus.
What are the charges of protons, electrons, and neutrons?
Protons are positively charged, electrons are negatively charged and neutrons have no charge.
What determines the chemical properties and stability of an atom?
The electron configuration of the atom determines the chemical properties of an element, whereas the nuclear structure characterizes the stability and radioactive decay of the nucleus of an atom.
What are the energy shells in an atom according to the Bohr atomic theory?
The Bohr atomic theory states that electrons in an atom rotate around the nucleus in discrete energy orbits or shells. These energy shells, referred to as the K shell, L shell, M shell, N shell, and so forth, are stationary and arranged in order of increasing energy.
What happens when there is a transition of an electron from an upper orbit to a lower orbit or vice versa?
When there is a transition of an electron from an upper orbit to a lower orbit, the energy difference between the two orbits is released as the photon radiation. If the electron is raised from a lower orbit to an upper orbit, the energy difference between the two orbits is absorbed and must be supplied for the transition to occur.
How are the energy shells and orbitals designated according to the quantum theory?
Each shell is designated by a quantum number n, called the principal quantum number, and denoted by integers. Each energy shell is subdivided into subshells or orbitals, which are designated as s, p, d, f, and so forth. For a principal quantum number n, there are n orbitals in the main shell.
How many electrons can each orbital and shell contain?
Each orbital can accommodate a maximum of 2(2l + 1) electrons, and the total number of electrons in a given shell is 2n^2. Thus, the K shell can contain only 2 electrons, the next L shell 8 electrons, the M shell 18 electrons, the N shell 32 electrons, and the O shell 50 electrons.
How are the orbitals filled in atoms?
In atoms, the orbitals are filled in order of increasing energy; that is, the lowest energy orbital is filled in first. However, when d orbitals start filling, there are some exceptions to this rule.
What determines the chemical properties of an element?
The electronic structure of the atom of an element determines to a large degree the chemical properties of the element.
How are elements arranged in the periodic table?
The periodic table has been devised to arrange the groups of elements of similar chemical properties in order of increasing atomic number. Each group contains elements of similar chemical properties, whereas the periods consist of elements having the same number of electron shells but dissimilar chemical properties.
What is the valence of an element?
The valence of an element is the tendency of the atom to lose or gain electrons to achieve a stable electron configuration. It is primarily determined by the number of electrons present in the outermost shell, referred to as the valence shell.
What is the octet rule in chemical bond formation?
All chemical bond formation is governed by the octet rule, which states that the electronic structure of each atom in a chemical bond assumes ns^2np^6 containing eight electrons, with the exception of hydrogen and lithium atoms, which essentially assume the structure 1s^2.
What is an electron volt (eV)?
An electron volt is the energy acquired by an electron accelerated through a potential difference of 1 V. The energy involved in chemical bond formation is of the order of a few electron volts (eV).
What is an Electrovalent or Ionic Bond?
An electrovalent or ionic bond is formed by the complete transfer of an electron from the valence shell of one atom to that of another atom. In ionic bonds, two oppositely charged ions are held together in the compound by coulombic forces.
How is NaCl formed?
In the formation of NaCl, the sodium atom loses one electron to become Na+, and the chlorine atom receives the electron to become Cl−. Both ions are then held by an electrovalent bond.
What is a Covalent Bond?
In covalent bonds, each of the two atoms participating in bond formation contributes one electron to the bond. Both electrons are shared equally by each atom and do not belong exclusively to one atom alone.
What is a Coordinate Covalent Bond?
In a coordinate covalent bond, the pair of electrons required for bond formation is donated by only one atom to another that can accommodate two electrons in octet formation. These bonds are also called semipolar bonds.
What is Complex Formation?
Metal complexes are produced by coordinate covalent bonds that are formed by the electrons donated by the chemical species having a lone pair of electrons. These complexes can be cationic, anionic, or neutral.
What are Ligands?
The molecules containing NH3, −CN, −SH, −COO, −NH2, CO, etc. are called ligands, which may be neutral or ionic in structure. They all possess an unshared pair of electrons that can be donated to a metal ion to form a complex.
What influences the stability of a metal complex?
The stability of a metal complex is influenced by the sizes of the metal ion and the ligand and the dipole moment of the ligand molecule. The smaller the size of the metal ion and the ligand, the more stable the coordinate covalent bond. Ligands with larger dipole moments form more stable complexes. The stability of a complex is also increased by chelation and the number of electron donor atoms in the chelating agent.
What are the components of an atom’s nucleus?
The nucleus of an atom is composed of protons and neutrons, collectively called nucleons.
What are the atomic number, neutron number, and mass number of an atom?
The number of protons in a nucleus is called the atomic number of the atom, denoted by Z. The number of neutrons is denoted by N. The total number of nucleons in a nucleus is referred to as the mass number, denoted by A. Thus, A is equal to Z + N.
What is the Bohr liquid drop model of the nucleus?
According to the Bohr liquid drop model, the nucleus is assumed to be spherical and composed of closely packed nucleons, and particle emission by the nucleus resembles evaporation of molecules from a liquid drop.
