What is the periodic trend for first ionization energy?
The first ionization energy varies in a predictable way across the periodic table. The ionization energy decreases from top to bottom in groups, and increases from left to right across a period.
Why does electron affinity increase across a period?
Electron affinity increases upward for the groups and from left to right across periods of a periodic table because the electrons added to energy levels become closer to the nucleus, thus a stronger attraction between the nucleus and its electrons.
What are compounds on the periodic table?
Compounds are composed of different elements in a fixed proportion. For example, 1 atom of sodium (Na) combines with 1 atom of chlorine (Cl) to form one molecule of sodium chloride (NaCl) compound. The elements in a compound do not always retain their original properties and cannot be separated by physical means.
How does ionization energy change across periods and down groups on the periodic table?
Ionization energy (IE) is the energy required to remove the highest-energy electron from a neutral atom. In general, ionization energy increases across a period and decreases down a group.
Why does ionization energy decrease moving down a group in the periodic table?
On the periodic table, first ionization energy generally decreases as you move down a group. This is because the outermost electron is, on average, farther from the nucleus, meaning it is held less tightly and requires less energy to remove.
Why does electron affinity increase from bottom to top?
The general trends of the electron affinity are that it increases from left to right across the periodic table due to an increase in the nuclear charge, and it increases from bottom to top due to the effect of atomic size.
Does electron affinity increase from top to bottom?
Electron affinity decreases from top to bottom within a group. This is caused by the increase in atomic radius.
How many compounds are there in chemistry?
Globally, more than 350,000 chemical compounds (including mixtures of chemicals) have been registered for production and use. A compound can be converted to a different chemical substance by interaction with a second substance via a chemical reaction.
How many chemical elements are there?
118
General observations. At present there are 118 known chemical elements.
How many compounds are there in the periodic table?
Because of the great variety of ways that carbon can bond with itself and other elements, there are more than nine million organic compounds. The compounds that are not considered to be organic are called inorganic compounds (see below Inorganic compounds).
How many periods are on the periodic table?
seven
The periodic table of the elements contains all of the chemical elements that have been discovered or made; they are arranged, in the order of their atomic numbers, in seven horizontal periods, with the lanthanoids (lanthanum, 57, to lutetium, 71) and the actinoids (actinium, 89, to lawrencium, 103) indicated …
What are the four categories of elements in the periodic table?
The elements in the periodic table are often divided into four categories: (1) main group elements, (2) transition metals, (3) lanthanides, and (4) actinides. The main group elements include the active metals in the two columns on the extreme left of the periodic table and the metals, semimetals,…
What is an element in chemistry?
Any substance that contains only one kind of an atom is known as an element. Because atoms cannot be created or destroyed in a chemical reaction, elements such as phosphorus (P 4 ) or sulfur (S 8) cannot be broken down into simpler substances by these reactions.
What are elements compounds and mixtures on the periodic table?
Elements, Compounds, and Mixtures. Most elements are metals, which are found on the left and toward the bottom of the periodic table. A handful of nonmetals are clustered in the upper right corner of the periodic table. The semimetals can be found along the dividing line between the metals and the nonmetals.
What is our research in physical chemistry?
In the symbolic domain our research in physical chemistry focuses on the ways in which student understanding is fostered in classrooms where discussion takes place using discourse analysis.