What is the primary basis for the arrangement of elements in the modern periodic table?
Increasing atomic number (number of protons).
How are elements with similar chemical properties positioned in the periodic table?
They are placed in the same vertical column, which is called a group.
How many vertical columns (groups) are there in the modern periodic table?
18.
How many horizontal rows (periods) are there in the modern periodic table?
7.
What determines the chemical properties of an element?
The number of valence electrons.
In what arrangement are elements placed on the periodic table?
In rows (periods) and columns (groups).
What is the name given to the elements in Group 1 of the periodic table?
Alkali metals.
What name is given to elements in Group 17 of the periodic table?
Halogens.
What is the common name for elements in Group 18?
Noble gases or inert gases.
What are the elements in between Group 2 and 13 called?
Transition elements.
What is the term for elements that have properties of both metals and non-metals?
Metalloids or semi-metals.
Do elements in the same group have the same or different numbers of valence electrons?
They have the same number of valence electrons.
What do elements in the same period have in common?
They have the same number of electron shells.
Are the Group 1 elements metals or nonmetals?
Metals.
Are the Group 17 elements metals or nonmetals?
Nonmetals.
What is the name for a gas that exists as single atoms?
Monatomic gases.
What is the trend of atomic size when moving from left to right across a period?
Atomic size decreases.
What is the trend of atomic size when moving down a group?
Atomic size increases.
What is the main characteristic of metalloids?
Semiconductivity.
Do the elements in a period have the same or different chemical properties?
Different.
Explanation Questions
Explain why arranging elements by increasing proton number is more effective than by atomic weight.
Arranging by proton number (atomic number) is more effective because it accurately groups elements with similar chemical properties together. While atomic weight provides a general order, it has inconsistencies due to isotopes and does not always align with chemical behaviour. The number of protons determines the electronic structure, and therefore, the chemical properties of an element.
Explain why elements in the same group have similar chemical properties.
Elements in the same group have the same number of valence electrons, which are the outermost electrons involved in chemical bonding. The number of valence electrons dictates how an element will react with other elements, thus leading to similar chemical properties.
Describe the relationship between the number of valence electrons and an element’s group number.
For main group elements (Groups 1, 2, and 13-18), the group number often corresponds to the number of valence electrons. For example, elements in Group 1 have 1 valence electron, Group 2 have 2, Group 13 have 3, and so on, until Group 18 with 8.
Explain what the terms “duplet” and “octet” mean in relation to electron configuration and why they are important.
A “duplet” refers to a stable outer shell of two electrons, which is achieved by elements like hydrogen and helium. An “octet” refers to a stable outer shell of eight electrons, achieved by most other elements. These full outer shells result in a stable, low-energy state, making these electron configurations important for understanding chemical stability and reactivity.
Why are noble gases (Group 18) generally unreactive?
Noble gases have a full valence shell, meaning they have either 2 (helium) or 8 (neon, argon, etc.) valence electrons. This full shell makes them exceptionally stable and not inclined to gain, lose, or share electrons, which is why they are generally unreactive.
Describe how metallic character changes across a period.
Metallic character decreases from left to right across a period. Elements on the left side of the period tend to be metals (readily lose electrons), those in the middle tend to be metalloids, and those on the right are nonmetals (tend to gain electrons). This is due to the increasing number of protons, which lead to stronger attraction of electrons in the valence shell.
Describe the change in atomic size across a period and explain the reasoning for this trend.
Atomic size generally decreases from left to right across a period. This is because as we move across a period, the number of protons and electrons increases, which draws the electron cloud closer to the nucleus. This stronger attraction reduces the atomic radius.
Describe the change in atomic size down a group, and explain the reasoning behind this trend.
Atomic size generally increases down a group. This is primarily because new electron shells are being added as we move down the group, causing the valence electrons to be further from the nucleus. Although the number of protons and electrons also increases, the addition of new electron shells has a more significant impact on the radius.
How do the properties of oxides change across a period, and why?
The properties of oxides generally change from basic to acidic as you move across a period. Oxides of metals on the left side tend to be basic, while oxides of nonmetals on the right side tend to be acidic. Some oxides in the middle exhibit amphoteric characteristics. This shift is due to the changing ability of elements to gain or lose electrons in the period.
What are metalloids and what is their significance in chemistry?
Metalloids, or semi-metals, are elements with properties intermediate between metals and nonmetals. They are important in chemistry because of their semiconducting properties. Silicon and germanium are used widely in electronics. They can also form both acidic and basic oxides, adding to their versatility.