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Questions and Answers
What is the primary basis for the organization of the modern periodic table?
What is the primary basis for the organization of the modern periodic table?
Which of the following groups includes Hydrogen?
Which of the following groups includes Hydrogen?
What is a characteristic of the elements found in the same group of the periodic table?
What is a characteristic of the elements found in the same group of the periodic table?
Which type of radius is defined as half the distance between the nuclei of two identical atoms bonded covalently?
Which type of radius is defined as half the distance between the nuclei of two identical atoms bonded covalently?
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Which block of the periodic table includes Groups 1 and 2?
Which block of the periodic table includes Groups 1 and 2?
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Which of the following correctly orders the types of atomic radii from largest to smallest?
Which of the following correctly orders the types of atomic radii from largest to smallest?
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What effect does the formation of an anion have on its ionic radius compared to its parent atom?
What effect does the formation of an anion have on its ionic radius compared to its parent atom?
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How does effective nuclear charge (Zeff) influence an electron in a multi-electron atom?
How does effective nuclear charge (Zeff) influence an electron in a multi-electron atom?
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What is the significance of the shielding constant (σ) in determining Zeff?
What is the significance of the shielding constant (σ) in determining Zeff?
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How does the order of the shielding effect among different orbital types rank?
How does the order of the shielding effect among different orbital types rank?
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Which group of elements does NOT belong to the category of noble metals?
Which group of elements does NOT belong to the category of noble metals?
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For an element with atomic number 110, which block does it fall under?
For an element with atomic number 110, which block does it fall under?
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Which of the following correctly describes the general trend in atomic radius across a period?
Which of the following correctly describes the general trend in atomic radius across a period?
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What determines the period number of an element if its atomic number is between 104 and 118?
What determines the period number of an element if its atomic number is between 104 and 118?
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When comparing isoelectronic species, which statement regarding atomic radius is correct?
When comparing isoelectronic species, which statement regarding atomic radius is correct?
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In the nomenclature system for elements with atomic numbers greater than 100, what suffix is used?
In the nomenclature system for elements with atomic numbers greater than 100, what suffix is used?
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Study Notes
Modern Periodic Table
- The modern periodic table is organized by increasing atomic number.
- It consists of 18 vertical columns (groups) and 7 horizontal rows (periods).
- Elements in the same group have similar chemical properties due to similar electronic configurations.
- The periodic table is based on the periodic law: the physical and chemical properties of elements are periodic functions of their atomic numbers.
Groups and Periods
- Group 1 (Alkali Metals): Li, Na, K, Rb, Cs, Fr. Hydrogen is not included in this group.
- Group 2 (Alkaline Earth Metals): Be, Mg, Ca, Sr, Ba, Ra.
- Group 13 (Boron Family): B, Al, Ga, In, Tl.
- Group 14 (Carbon Family): C, Si, Ge, Sn, Pb.
- Group 15 (Nitrogen Family/Pnictogens): N, P, As, Sb, Bi.
- Group 16 (Oxygen Family/Chalcogens): O, S, Se, Te, Po.
- Group 17 (Halogens): F, Cl, Br, I, At.
- Group 18 (Noble Gases/Inert Gases): He, Ne, Ar, Kr, Xe, Rn.
Blocks in the Periodic Table
- s-block: Groups 1 and 2. General electronic configuration: ns1-2.
- p-block: Groups 13-18. General electronic configuration: ns2np1-6.
- d-block: Groups 3-12. General electronic configuration: (n-1)d1-10ns0-2.
- f-block: Lanthanides (period 6, group 3, 58-71) and Actinides (period 7, group 3, 90-103). Lanthanum (57) and Actinium (89) are considered d-block elements, not f-block.
Atomic Radius
- Atomic radius is the distance between the nucleus and the outermost electron. It cannot be directly measured.
- Covalent radius: Half the distance between the nuclei of two identical atoms bonded covalently.
- Metallic radius: Half the distance between the nuclei of two adjacent atoms in a metallic crystal.
- Van der Waals radius: Half the distance between the nuclei of two identical atoms that are not bonded, but are close together. Generally defined for noble gases.
- The order of atomic radii is generally Van der Waals > Metallic > Covalent.
Ionic Radius
- Ionic radius is the distance between the nucleus and the outermost electron in an ion.
- Cations: Smaller than their parent atoms due to electron loss.
- Anions: Larger than their parent atoms due to electron gain.
- The ratio of atomic number (Z) to the number of electrons (e) determines the size of an ion: A higher Z/e ratio results in a smaller ionic radius.
Effective Nuclear Charge (Zeff) and Shielding Effect
- Zeff represents the net positive charge experienced by an electron in a multi-electron atom.
- Zeff = Z - σ (where Z is the atomic number and σ is the shielding constant).
- Shielding effect: Inner electrons reduce the attractive force of the nucleus on outer electrons.
- Shielding effect follows the order: s > p > d > f.
Periodic Properties
- Ionization Energy: The energy required to remove an electron from a gaseous atom.
- Electron Affinity: The energy change when an electron is added to a gaseous atom.
- Electronegativity: The ability of an atom to attract electrons in a chemical bond.
Nomenclature of Elements with Atomic Number > 100
- Elements with atomic numbers greater than 100 are named using a system based on roots for the digits 0-9 (nil, un, bi, tri, quad, pent, hex, sept, oct, enn) followed by "-ium". The conventions differ slightly from organic chemistry nomenclature.
Identifying Period, Group, and Block from Atomic Number
- Step 1: Check if the atomic number falls within the lanthanide (58-71) or actinide (90-103) series. If so, the period, group, and block are known.
- Step 2: If the atomic number is between 104 and 118, the period is 7; the group is (atomic number - 100); the block is determined from the group number (3-12: d-block; 13-18: p-block).
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Step 3 (General Rule):
- Period: Determined by the next highest noble gas.
- Group: (Atomic number + 18) - (Atomic number of the next highest noble gas) (Add 14 if the result is negative).
- Block: Determined from the group number (1 or 2: s-block; 3-12: d-block; 13-18: p-block). Note that the f-block elements (lanthanides and actinides) are treated separately in step 1.
Noble Metals
- Noble metals are elements in groups 8-11 (excluding the first element in each group). They are resistant to oxidation.
Atomic Radius
- Atomic size is inversely proportional to positive charge and directly proportional to negative charge. This relationship is most useful when comparing isoelectronic species (species with the same number of electrons).
- When comparing ions with the same number of electrons, the ion with the highest positive charge will have the smallest radius, and the ion with the highest negative charge will have the largest radius.
- Across a period, atomic radius generally decreases due to increasing effective nuclear charge.
- Down a group, atomic radius generally increases due to the addition of electron shells.
- An exception to the general trend of atomic radius occurs in Group 13, where the atomic radius of gallium is smaller than that of aluminum due to poor shielding of the d electrons.
Ionic Radius
- The trend of ionic radius follows the same principles as atomic radius: across a period, it generally decreases, and down a group, it generally increases.
- Isoelectronic species should be evaluated based on their charge: higher positive charge means smaller ionic radius.
Ionization Energy
- Ionization energy is the minimum energy required to remove an electron from an isolated, gaseous atom in its ground state.
- Successive ionization energies (I₁, I₂, I₃, etc.) always increase for a given element because removing an electron from an increasingly positive ion requires more energy.
- A large jump in successive ionization energies indicates the removal of an electron from a stable electron configuration (e.g., a noble gas configuration). The number of valence electrons is one less than the ionization energy level at which the large jump occurs.
Electron Affinity
- Electron affinity is the tendency of a gaseous atom to gain an electron. Higher electron affinity indicates a greater tendency to gain an electron.
- Electron affinity is often measured by the electron gain enthalpy (ΔH). A negative ΔH value signifies an exothermic process (energy released), while a positive ΔH value signifies an endothermic process (energy absorbed).
- Most elements have a negative first electron gain enthalpy (exothermic). The second electron gain enthalpy is usually positive (endothermic) due to electron-electron repulsion in the anion.
- Exceptions to the general trend of electron affinity exist. Noble gases, nitrogen, beryllium, and magnesium have positive first electron gain enthalpies because adding an electron disrupts a stable electron configuration.
Electronegativity
- Electronegativity is the tendency of an atom in a molecule to attract shared electrons toward itself.
- Electronegativity generally increases across a period and decreases down a group.
- Fluorine has the highest electronegativity (4.0 on the Pauling scale); cesium has the lowest (0.7).
- The electronegativity values for elements in the second and third periods are often memorized for problem-solving.
- In some cases, the relative electronegativity of elements from the second period can deviate from the general trend due to the smaller size and increased electron-electron repulsion. Specifically, for the second period elements (B, C, N, O, F), electronegativity often increases from left to right, but the electronegativity of fluorine is slightly lower than oxygen. Chlorine has the highest electron affinity among all elements.
Modern Periodic Table Organization
- Organized by increasing atomic number.
- 18 vertical columns (groups) and 7 horizontal rows (periods).
- Elements in the same group share similar chemical properties due to similar electron configurations.
- Based on the periodic law: properties are periodic functions of atomic numbers.
Key Groups
- Group 1 (Alkali Metals): Li, Na, K, Rb, Cs, Fr (Hydrogen excluded).
- Group 2 (Alkaline Earth Metals): Be, Mg, Ca, Sr, Ba, Ra.
- Group 13 (Boron Family): B, Al, Ga, In, Tl.
- Group 14 (Carbon Family): C, Si, Ge, Sn, Pb.
- Group 15 (Pnictogens): N, P, As, Sb, Bi.
- Group 16 (Chalcogens): O, S, Se, Te, Po.
- Group 17 (Halogens): F, Cl, Br, I, At.
- Group 18 (Noble Gases): He, Ne, Ar, Kr, Xe, Rn.
Periodic Table Blocks
- s-block: Groups 1 and 2 (ns1-2 electron configuration).
- p-block: Groups 13-18 (ns2np1-6 electron configuration).
- d-block: Groups 3-12 ((n-1)d1-10ns0-2 electron configuration).
- f-block: Lanthanides (period 6, 58-71) and Actinides (period 7, 90-103). Note that Lanthanum (57) and Actinium (89) are d-block elements.
Atomic Radius
- Distance between the nucleus and outermost electron. Cannot be directly measured.
- Covalent radius: Half the distance between nuclei of two covalently bonded identical atoms.
- Metallic radius: Half the distance between nuclei of adjacent atoms in a metallic crystal.
- Van der Waals radius: Half the distance between nuclei of two identical, non-bonded, closely-spaced atoms (often for noble gases).
- General order: Van der Waals > Metallic > Covalent.
Ionic Radius
- Distance between the nucleus and outermost electron in an ion.
- Cations: Smaller than parent atoms due to electron loss.
- Anions: Larger than parent atoms due to electron gain.
- Size determined by Z/e ratio (higher ratio means smaller radius).
Effective Nuclear Charge (Zeff) and Shielding
- Zeff: Net positive charge experienced by an electron. Zeff = Z - σ (Z = atomic number, σ = shielding constant).
- Shielding effect: Inner electrons reduce nuclear attraction on outer electrons.
- Shielding order: s > p > d > f.
Periodic Properties
- Ionization Energy: Energy to remove an electron from a gaseous atom.
- Electron Affinity: Energy change upon adding an electron to a gaseous atom.
- Electronegativity: Atom's ability to attract electrons in a bond.
Naming Elements (Z > 100)
- Use roots for digits 0-9 (nil, un, bi, tri, quad, pent, hex, sept, oct, enn) + "-ium". Conventions differ slightly from organic chemistry.
Identifying Period, Group, and Block from Atomic Number
- Step 1: Check for lanthanides (58-71) or actinides (90-103).
- Step 2: If Z is 104-118: period 7, group (Z - 100), block determined from group.
- Step 3 (General): Period (next highest noble gas), Group [(Z + 18) - (noble gas Z)] (add 14 if negative), Block (from group number: 1,2 = s; 3-12 = d; 13-18 = p). f-block is treated separately in step 1.
Noble Metals
- Groups 8-11 (excluding the first element in each group). Resistant to oxidation.
Atomic Radius Trends
- Inversely proportional to positive charge, directly proportional to negative charge (isoelectronic species comparison).
- Across a period: generally decreases (increasing Zeff).
- Down a group: generally increases (additional electron shells). Note: exceptions exist.
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Description
Test your knowledge of the modern periodic table and its organization by atomic number. This quiz covers groups, periods, and the properties of elements, highlighting trends in the periodic law. Dive into the specifics of alkali metals, noble gases, and more!
