אטום הגדרה - Google Search

What is the definition of an atom according to the lecture notes?

The smallest particle of a chemical element that retains the properties of that element, serving as the basic building block of all matter in the world (solid, liquid, or gas).

What are the three main subatomic particles that make up an atom?

Protons (positively charged), neutrons (neutral / no charge), and electrons (negatively charged).

What constitutes the atomic nucleus, and which specific atom lacks neutrons in its nucleus?

The nucleus is a dense central region containing protons and neutrons; a regular hydrogen atom is the sole exception, possessing only $1$ proton and no neutrons.

What fundamental force prevents positively charged protons in the nucleus from repelling each other and flying apart?

The strong nuclear force.

What percentage of an atom's volume is composed of empty space?

More than $99.9\%$ of an atom's volume is empty space.

How does the mass of an electron compare to that of a proton or neutron?

An electron's mass is approximately $1{,}836$ times smaller than that of a proton or neutron, making its contribution to the overall atomic mass negligible.

Unlike the elementary electron, what smaller subatomic particles compose a proton?

Three quarks: two "up" quarks and one "down" quark.

What characterizes an electrically neutral atom?

An atom whose net electrical charge is $0$ because its number of positively charged protons ($+1$ each) equals its number of negatively charged electrons ($-1$ each).

What is the atomic number ($Z$) and why is it essential?

The atomic number ($Z$) is the count of protons in the nucleus; it acts as the element's unique identity card and determines its sequential position in the periodic table.

What is the Hebrew term for molecule and how is a molecule defined?

Peruda (פְּרוּדָה); the smallest particle of a substance that can exist independently while retaining its chemical properties, consisting of two or more atoms bound by chemical bonds.

What is the structural difference between a molecule of an element and a molecule of a compound?

A molecule of an element consists of identical atoms of the same element (e.g., $\text{O}_2$), whereas a molecule of a compound consists of atoms from two or more different elements (e.g., $\text{H}_2\text{O}$).

What defines a chemical compound and how can it be separated into its constituent elements?

A pure substance formed of two or more different elements bonded chemically in a fixed numerical ratio; it can only be separated via chemical reactions or energy investment (such as electrolysis), not physical methods.

What are the ancient Latin roots for the chemical symbols $\text{Fe}$, $\text{Au}$, and $\text{Na}$?

$\text{Fe}$ derives from Ferrum (iron), $\text{Au}$ from Aurum (gold), and $\text{Na}$ from Natrium (sodium).

Why is exact letter capitalization critical when writing chemical symbols such as $\text{Co}$ versus $\text{CO}$?

The first letter is always uppercase and the second lowercase; therefore, $\text{Co}$ signifies the single element cobalt, whereas $\text{CO}$ represents the compound carbon monoxide.

What is a cation (positive ion) and which group of elements typically forms one?

An atom that has lost one or more electrons, giving it a net positive charge (e.g., $\text{Na}^+$, $\text{Ca}^{2+}$); cations are primarily formed by metals.

What is an anion (negative ion) and which group of elements typically forms one?

An atom that has gained one or more electrons, giving it a net negative charge (e.g., $\text{Cl}^-$, $\text{O}^{2-}$); anions are primarily formed by non-metals.

What are the maximum electron capacities for energy levels (shells) $1$, $2$, $3$, and $4$?

Level $1$ can hold up to $2$ electrons, level $2$ up to $8$, level $3$ up to $18$, and level $4$ up to $32$ electrons.

What is the octet rule in electron arrangement?

The tendency of atoms to attain maximum stability by filling their outermost energy shell with $8$ valence electrons (or $2$ electrons for smaller atoms like hydrogen and helium).

What are the four subshell types ($s, p, d, f$) and their respective orbital counts and maximum electron capacities?

Subshell $s$ has $1$ orbital ($2$ electrons), $p$ has $3$ orbitals ($6$ electrons), $d$ has $5$ orbitals ($10$ electrons), and $f$ has $7$ orbitals ($14$ electrons).

Why do electrons populate the $4s$ subshell before entering the $3d$ subshell?

The $4s$ subshell requires a lower amount of energy to occupy than the $3d$ subshell, and electrons consistently occupy the lowest available energy level first.

What fundamental structural feature does a period (row) number indicate in the periodic table?

The total number of occupied electron energy shells present in an atom of that element in its ground state.

Why does atomic radius decrease as one moves from left to right across a single period in the periodic table?

Protons are added to the nucleus alongside electrons in the same shell; the greater positive nuclear charge exerts a stronger electrostatic pull, drawing the electron cloud inward.

What are the key chemical characteristics of Group 1 (alkali metals) and Group 17 (halogens)?

Group 1 metals have $1$ valence electron, are soft, and react violently with water; Group 17 halogens have $7$ valence electrons, are highly active toxic non-metals, and their name means "salt formers".

What is the electron arrangement across energy levels $1$ through $7$ for Oganesson ($Z = 118$)?

$2, 8, 18, 32, 32, 18, 8$, demonstrating that even the heaviest Period 7 element possesses exactly $7$ energy levels.

Which four non-metallic elements constitute approximately $96\%$ of human body mass?

Oxygen, carbon, hydrogen, and nitrogen.