atomic-physicsatomselectromagnetism
The atoms in my table "stick together" to form a rectangle. Why? What makes them stick together?
I know about ionic/covalent bonding etc., but consider a sheet of pure iron. Just atoms of one element. The atoms still stick together to form a sheet instead of being "everywhere".But if I place ten balls on the ground beside each other they are completely independent of each other.
So what "connects" the atoms?
These are all good questions! Based on your description I assume you haven't had an introduction to solid state physics yet? Let's take your image of an electron that "jumps"
from atom to atom. In my understanding I wouln't describe it that way, to me it's a wavefunction of the electron that is almost independent from the valence electrons and you
can use the free electron gas approximation. Why is this band independent? See the following picture for an intuitive understanding how the atomic potentials define the possible energy levels within a periodic arrangement of atoms:
I think most of your questions will be easier to answer if you make yourself familiar with basic concepts and approximations people use to describe electrons in a solid first. Sure, a lot of things can be understood if we consider electrons to be little spheres that scatter from bigger spheres (ions), but you said you want to understand on the atomic level -> it's good to see the electron as a wave and see how this wave behaves in a lattice with certain boundary conditions.
First, I would read about a crystal. Atoms are arranged in a periodic lattice (assume a nice crystal for a first simple picture) and you can make assumptions based on this periodicity. You can define a unit cell and the Brillouin zone. You will see that the energy levels will sometimes split up in different bands and based on the filling of these bands you end up wih a metal, insulator etc. Electrons are fermions, can two electrons be in the same state? This defines the Fermi velocity.
This filling of the available energy levels describes the Fermi surface, a very useful tool to describe other more advanced concepts. Then you will see what happens if you change the arrangements of the atoms or why in different spatial directions electrons can move due to the bonding of different atomic orbitals.
This could be a good start ; ) -> http://britneyspears.ac/lasers.htm
There are other introductions out there, most of them describe the basics really well.
He is a noble gas. It has a completely filled 1s shell. Li has one electron more that resides in the 2sp shell. Be has 2 electrons in this shell. Both atoms therefore have an unfilled valence shell, are analogous for example Na and Mg, also both metals.
Best Answer
Consider two $H$ atoms $rotating^{(1)}$ about their centre of mass, now both the atoms are electrically neutral and far apart so thay neither strong nor weak nuclear force comes into consideration. If they were to stay in this state only then they would never combine and form $H_2$ but what happens is that when the electrons of each atom are moving during various instances dipoles are formed and london dispersion forces come into play due to these interactions the 2 atoms move towards each other and at a certain distance acheive a stable equilibrium, and are therefore bonded to each other.
On the other hand lets suppose you somehow got 2 balls of $H$ in elemental form and placed them near each other, the atoms of both ball will still get induced dipoles but since all the dipoles are randomly oriented, their would not be any significant overall dipole moment which may force the two balls to come close and join.
This was highly simplified version of what happens with iron and other elements and compounds, on thd atomic scale considerable dipole moments are developed even in neutral atoms/compounds , these motivate the further bonding to form other objects such as lattices, crystals, sheets and so on. On the other hand at the macro scale, no considerable attraction forcd develops between two neutral objects which may motivate them to join/bond. But indeed if you have to oppoisitely charged objects they may join together. Also to join objects on macroscales we have different proceses such as different types of welding etc
$(1)$ I said rotating about centre of mass to avoid considering attraction due to gravitational interaction between the two atoms.