Using the Pen/Bezier tool
, click once to start the path, move the mouse to where you want to end the path, and double-click to end the path. That creates a straight, 2-node path.
Then switch to the Node tool
. Position the pointer directly on top of that path, approximately halfway between the nodes of the path. You can drag the path to create the curve.
That will create a fairly rough representation of what you want. If you want more precision, this is what I would do.
1 -- create the 2 node path with Pen/Bezier tool
2 -- switch to the Node tool
3 -- instead of dragging the curve, double-click on the path, to create a new node
(Or if you want super-precision, instead of double-clicking on the path to create the new node, click once on the path to select both nodes. Then click this button on the Node tool control bar, to add a new node, which is precisely at the halfway point between the 2 original nodes
)
4 -- change the node to a smooth node (this button on the Node tool control bar
) (or there's probably a key shortcut, which you can find at Help menu > Key and Mouse Reference)
5 -- using the Node tool, you can drag the node slightly (if you want more precision, you can use arrow keys to move a selected node, or on the control bar, you can set precisely the x,y coordinates for the node)
6 -- if the curve isn't quite right, you can adjust the handles of the node
For the ends of all the paths, you can either hide them under the atoms, or you can set up a situation where you can snap the ends of the path (nodes) to the edge of the atoms. If you need to be super precise, there are a few different ways that could be accomplished.
I guess I would probably use Guides to create the snapping points. You can drag horizontal or vertical guides right out of the respective rulers. You can double-click on a guide to open a small dialog with which you can precisely place the guide (this includes either x,y coordinates, or relative placements). Or the guide can snap to various parts of the atoms, depending on how they are made - handles, if they are still circles, or nodes if they are paths, rotation centers, grid (If you were using a grid), etc. (You don't need it for this image, but for future reference, guides can be rotated to any angle. And if, when you drag them out of the rulers, you start dragging near the corners, guides at 45° angle are created automatically.)
I think I've given you enough info to do what you want. But if you get stuck, or don't understand something....or you need different info, please feel free to ask
