What Does the Group/family Number Tell Us About Atoms of Elements?
The Periodic Tabular array
The periodic tabular array shows all the elements and their physical backdrop; it is arranged based on diminutive numbers and electron configurations.
Learning Objectives
Place the mutual periodic trends that tin be deduced from the periodic table of elements
Key Takeaways
Key Points
- The periodic table lists all the elements, with information nearly their atomic weights, chemic symbols, and diminutive numbers.
- The system of the periodic table leads us to visualize sure trends among the atoms.
- The vertical columns (groups) of the periodic table are bundled such that all its elements accept the same number of valence electrons. All elements inside a certain group thus share similar backdrop.
Cardinal Terms
- atomic number: The number, equal to the number of protons in an cantlet, that determines its chemic properties. Symbol: Z
- grouping: A vertical cavalcade in the periodic table, which signifies the number of valence shell electrons in an element'due south atom.
- catamenia: A horizontal row in the periodic table, which signifies the total number of electron shells in an element's atom.
Element Symbols
The periodic table is structured as an xviii Ten 7 grid, positioned above a smaller double row of elements. The periodic table only lists chemical elements, and includes each isotope of each element within one cell. In the typical periodic tabular array, each element is listed by its element symbol and atomic number. For instance, "H" denotes hydrogen, "Li" denotes lithium, so on. Most elements are represented past the start letter or first 2 letters of their English name, but there are some exceptions. Two notable exceptions include silver and mercury. The symbol for silver is "Ag" from Latin argentum, which means "gray" or "shining." The symbol for mercury is "Hg" from the Latinized Greek hydrargyrum, which means "water-silver." Many periodic tables include the full name of element every bit well and color-code the elements based on their phase at room temperature (solid, liquid, or gas).
The periodic tabular array: The periodic table is a tabular brandish of all the chemic elements. The atoms are grouped in club of increasing atomic number.
Rows and Periods
The chemical element symbol is always almost accompanied by other data such as atomic number and diminutive weight. Atomic number describes the number of protons in 1 atom of that element. For example, an atom of oxygen contains 8 protons. Elements are listed in guild of increasing atomic number from left to right. Each row of the periodic table is chosen a menstruation and each column of the periodic table is chosen a group (or family unit). Some groups accept specific names similar the halogens or noble gases. Elements within the same period or group have similar properties.
Determining Chemical Properties using the Periodic Table
Chemical properties of each element are determined by the element's electronic configuration, and particularly by its outermost valence electrons. An element'due south location in the periodic table is largely dependent on its electrons; the number of valence shell electrons determines its group, and the type of orbital in which the valence electrons lie in determines the element's block. In addition, the full number of electron shells an atom determines which period it belongs to. Because of its structure, the periodic table has become an extremely useful tool for assessing and predicting elemental and chemical trends.
Molecules
Molecules are electrically neutral compounds made of multiple atoms bound together by chemical bonds.
Learning Objectives
Recognize the general properties of molecules
Key Takeaways
Primal Points
- Molecules are neutral and do not carry any charge.
- A molecule may consist of nonmetallic atoms of a single chemical element, equally with oxygen (Oii), or of different elements, as with water (H2O).
- The geometry and composition of a molecule will determine its chemical and physical properties.
- Isomers are molecules with the same atoms in different geometric arrangements.
Fundamental Terms
- covalent: when ii or more nonmetallic atoms are bound together by sharing electrons.
- isomer: Molecules with the same number of atoms in different geometric arrangements.
- chemical compound: when two or more different atoms are held together by a covalent bond. All compounds are molecules only not all molecules are compounds.
- molecule: Two or more than atoms that are held together past a chemical covalent bond.
Atoms and Molecules
An atom is defined as a basic unit of matter that contains a centralized dense nucleus surrounded by an electron cloud. When two or more atoms are held together by a chemical covalent bond, this new entity is known as a molecule. The discussion "molecule" is a loose term, and it colloquially carries different meanings across different fields of study. For example, the term "molecules" is used in the kinetic theory of gases, referring to any gaseous particle regardless of its limerick.
Well-nigh often, the term "molecules" refers to multiple atoms; a molecule may be composed of a single chemical element, as with oxygen (O2), or of multiple elements, such as water (H2O). Molecules are neutral and carry no accuse; this property distinguishes them from polyatomic ions, such as nitrate (NO3 –).
caffeine molecule: Caffeine is a complicated molecule, composed of many atoms bonded to each other in a specific arrangement.
Molecular size varies depending on the number of atoms that make up the molecule. Most molecules are too small to be seen with the naked eye. The smallest molecule is diatomic hydrogen (H2), with a bond length of 0.74 angstroms. Macromolecules are big molecules composed of smaller subunits; this term from biochemistry refers to nucleic acids, proteins, carbohydrates, and lipids. Some macromolecules may be observed past specialized microscopes.
Oft, a chemical compound 's limerick can too exist denoted past an empirical formula, which is the simplest integer ratio of its constituent chemical elements. However, this empirical formula does non e'er describe the specific molecule in question, since it provides only the ratio of its elements. The full elemental composition of a molecule tin can exist precisely represented by its molecular formula, which indicates the exact number of atoms that are in the molecule.
Example
- C6H12O6 = molecular formula for glucose
- CH2O = empirical (simplified ratio) formula for glucose
Isomers
Isomers are molecules with the same atoms in different geometric arrangements. Considering of these dissimilar arrangements, isomers often take very dissimilar chemical and concrete properties. In the picture below, i-propanol is mostly used in the synthesis of other compounds and has a less offensive odor, whereas 2-propanol is the mutual household alcohol.
propanol structural isomers: The chemic formula for propanol (C3H7OH) describes several unlike molecules, which vary by the position of the alcohol (OH). Each molecule is a structural isomer of the other.
Ions
An ion is an atom or molecule that has a internet electrical charge because its total number of electrons is non equal to its number of protons.
Learning Objectives
Compare the unlike classes of ions
Cardinal Takeaways
Key Points
- Ions are formed when the number of protons in an atom does not equal the number of electrons. If more protons are nowadays, the ion is positive and is known every bit a cation; if more electrons are present, the ion is negative and referred to every bit an anion.
- Ions are highly reactive species. They are by and large institute in a gaseous land and practice not occur in affluence on Earth. They are repelled by like electrical charges and are attracted to opposite charges.
- The electron cloud of an atom determines the size of the atom; added electrons (anions) increase the electron repulsion, increasing the ion's size, while cations (with less electrons) are smaller than the atom because at that place are fewer electrons in the cloud to repel each other.
Fundamental Terms
- ion: An cantlet or group of atoms bearing an electrical accuse, such equally the sodium and chlorine atoms in a salt solution.
- anion: Ions that are negatively charged because they have more electrons than protons.
- cation: Ions that are positively charged because they take more protons than electrons.
An atom is a bones unit of thing that consists of a dense nucleus composed of positively charged protons and neutral neutrons, which is surrounded by a deject of negatively charged electrons. If an atom has the same number of protons and electrons, it is electronically neutral. However, if the total number of electrons does not equal the number of protons, the atom has a net electrical charge.
Any atom or molecule with a net accuse, either positive or negative, is known every bit an ion. An ion consisting of a single atom is a monoatomic ion; an ion consisting of ii or more atoms is referred to equally a polyatomic ion. The positive electric charge of a proton is equal in magnitude to the negative charge of an electron; therefore, the net electric charge of an ion is equal to its number of protons minus its number of electrons.
Ions are highly reactive species. They are generally found in a gaseous state and do not occur in abundance on Earth. Ions in the liquid or solid land are produced when salts collaborate with their solvents. They are repelled past like electric charges and are attracted to opposite charges.
Types of Ions
There are specialized types of ions. Anions accept more electrons than protons and and so have a net negative charge. Cations have more protons than electrons then have a net positive charge. Zwitterions are neutral and take both positive and negative charges at different locations throughout the molecule. Anions are generally larger than the parent molecule or cantlet, because the backlog electrons repel each other and add to the concrete size of the electron cloud. Cations are by and large smaller than their parent atom or molecule due to the smaller size of their electron clouds.
Hydrogen ions: The relationship betwixt a molecule, its cation, and its anion is shown.
An ion is denoted by writing its net negative charge in superscript immediately after the chemical structure for the atom/molecule. Conventionally the internet charge is written with the magnitude before the sign; the magnitude of singly charged molecules/atoms is generally omitted. Monoatomic ions are sometimes also represented by Roman numerals, which designate the formal oxidation country of the element, whereas the superscripted numerals denote the cyberspace charge. For instance, Atomic number 262+ tin be referred to as Fe(II). These representations can be idea of as equivalent for monoatomic ions, but the Roman numerals cannot be applied to polyatomic ions.
Forming Ions
Ions can exist formed past ionization, which is the procedure of a neutral atom losing or gaining electrons. Generally, the electrons are either added to or lost from the valence vanquish of an atom; the inner-shell electrons are more than tightly jump to the positively charged nucleus and so practise not participate in this type of chemical interaction.
Ionization generally involves a transfer of electrons between atoms or molecules. The process is motivated by the accomplishment of more stable electronic configurations, such as the octet dominion, which states that most stable atoms and ions have 8 electrons in their outermost (valence) shell. Polyatomic and molecular ions can besides exist formed, mostly by gaining or losing elemental ions, such as H+, in neutral molecules. Polyatomic ions are by and large very unstable and reactive.
An common example of an ion is Na+. Sodium has a +one charge because sodium has eleven electrons. However, according to the octet rule, sodium would exist more than stable with ten electrons (two in its inner almost shell, 8 in its outermost shell). Therefore, sodium tends to lose an electron to become more stable. On the other paw, chlorine tends to gain an electron to become Cl–. Chlorine naturally has 17 electrons but it would be more stable with 18 electrons (2 in its inner most shell, 8 in its 2nd shell, and viii in its valence shell). Therefore, chlorine volition take an electron from another atom to become negatively charged.
Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/the-periodic-table/
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